Armando Basso

Gene expression profiling of the hedgehog signaling pathway in human meningiomas

The Hedgehog (Hh) signaling pathway has an important role during embryogenesis and in adult life, regulating proliferation, angiogenesis, matrix remodeling and stem-cell renewal. Deregulation of the Hh pathway is involved in tumor development, since mutations in several components of this pathway were found in patients with basal cell carcinoma, medulloblastoma and other tumors; however, the role of Hh in meningiomas has not been studied yet. Meningiomas represent 30% of primary cranial tumors, are mostly benign and prevail in the second half of life. Novel therapies for meningiomas such as targeted molecular agents could use Hh pathway components. To provide information concerning molecular alterations, by use of real-time RT-PCR, we studied expression at the mRNA level of 32 Hh pathway and target genes in 36 meningioma specimens of different grades. mRNA levels of 16 genes, involved mainly in Hh pathway activation and cell proliferation, increased in meningiomas in comparison with normal tissue, whereas those of 7 genes, mainly related to Hh pathway repression, decreased. The most significant changes occurred in signal transduction (SMO) and GLI-transcription factor genes, and the target FOXM1 mRNA attained the highest values; their overexpression was found in aggressive and in benign tumors. Some proliferation-related genes (SPP1, IGF2) were overexpressed in higher meningioma grades. A correlation in expression between genes with a similar function was also found. Our results show a marked activation of the Hh pathway in meningiomas, which may be important for their biological and clinical characterization and would be useful for gene therapy.

Gene Expression Profiling of ErbB Receptors and Ligands in Human Meningiomas

ErbB family receptors mediate major cellular functions implied in tumorigenesis, though their role in meningiomas was not thoroughly studied. Meningiomas represent 30% of primary cranial tumors, are mostly benign, and prevail in the second half of life. Tumor therapy requires information about molecular alterations, thus we studied expression of ErbB receptor and ligand genes by real-time RT-PCR in different meningioma grades. Receptors were overexpressed (ErbB1, ErbB2) or underexpressed (ErbB3, ErbB4). Ligands EGF, TGFA, AREG, DTR, BTD were underexpressed and the neuregulins were overexpressed or underexpressed. A strong ErbB1–ErbB2 correlation was found. These data might be useful for gene therapy.

Expression of p16 INK4A gene in human pituitary tumours

Pituitary adenomas comprise 10–15% of primary intracranial tumours but the mechanisms leading to tumour development are yet to be clearly established. The retinoblastoma pathway, which regulates the progression through the cell cycle, is often deregulated in different types of tumours. We studied the cyclin-dependent kinase inhibitor p16INK4A gene expression at mRNA level in human pituitary adenomas. Forty-six tumour specimens of different subtypes, 21 clinically non-functioning, 12 growth hormone-secreting, 6 prolactin-secreting, 6 adrenocorticotropin-secreting, and 1 thyrotropin-secreting tumours were studied. All clinically non-functioning and most of the hormone-secreting tumours were macroadenomas (38/46). The RT–PCR assay and electrophoresis of the PCR-products showed that p16INK4A mRNA was undetectable in: 62% of non-functioning, 8% of growth hormone-secreting, 17% of prolactin-secreting and 17% of adrenocorticotropin-secreting adenomas. Forty percent of all macroadenomas and 25% of microadenomas had negative p16INK4A mRNA, the latter results suggest that the absence of p16INK4A product might be an early event in tumours with no expression of this suppressor gene. Within the non-functioning adenomas 63% were “null cell” and 37% were positive for some hormone, both subgroups showed similar percentage of cases with absence of p16INK4A mRNA. Our results show that clinically non-functioning macroadenomas have impaired p16INK4A expression in a clearly higher proportion than any other pituitary tumour subtype investigated. Other regulatory pathways may be implicated in the development of tumours with positive p16INK4A expression.

NF2 tumor suppressor gene : a comprehensive and efficient detection of somatic mutations by denaturing HPLC and microarray-CGH

The NF2 tumor suppressor gene, located in chromosome 22q12, is involved in the development of multiple tumors of the nervous system, either associated with neurofibromatosis 2 or sporadic ones, mainly schwannomas and meningiomas. In order to evaluate the role of the NF2 gene in sporadic central nervous system (CNS) tumors, we analyzed NF2 mutations in 26 specimens: 14 meningiomas, 4 schwannomas, 4 metastases, and 4 other histopathological types of neoplasms. Denaturing high performance liquid chromatography (denaturing HPLC) and comparative genomic hybridization on a DNA microarray (microarray- CGH) were used as scanning methods for small mutations and gross rearrangements respectively. Small mutations were identified in six out of seventeen meningiomas and schwannomas, one mutation was novel. Large deletions were detected in six meningiomas. All mutations were predicted to result in truncated protein or in the absence of a large protein domain. No NF2 mutations were found in other histopathological types of CNS tumors. These results provide additional evidence that mutations in the NF2 gene play an important role in the development of sporadic meningiomas and schwannomas. Denaturing HPLC analysis of small mutations and microarray-CGH of large deletions are complementary, fast, and efficient methods for the detection of mutations in tumor tissues.

Surgical treatment of cervical spine fibrous dysplasia: technical case report and review

OBJECTIVES AND IMPORTANCE: Cervical spine compromise by fibrous dysplasia is rare; only 20 cases have been reported. Treatment was surgical in six cases, but the management differed among the other cases. In this retrospective case report, we analyze and discuss the surgical treatment of this condition in the context of previous reports. CLINICAL PRESENTATION: A 35 year-old woman presented 1 week after the onset of spontaneous neck and left arm pain, which increased 48 hours later. A physical examination revealed only slight neck stiffness. Her previous history was unremarkable. Plain radiographic, radioisotope bone scanning, and computed tomographic studies were performed. The body of the fifth cervical vertebra was collapsed. INTERVENTION: A C5 corpectomy was performed, and the spine was reconstructed with a block of biocompatible osteoconductive polymer and a plate with four bicortical screws. Pathologic examination revealed fibrous dysplasia. The postoperative course was uneventful, and the pain disappeared. Radiographs obtained postoperatively demonstrated good spinal alignment. The patient was discharged after 7 days. Three years later, she continued to have no pain, and spine stability was preserved. CONCLUSION: Good results can be achieved in the surgical treatment of dysplastic tissue with the use of instruments for spine reconstruction and synthetic grafting to prevent invasion.

The transzygomatic approach

We aim to describe the technical details of the transzygomatic approach to intracranial surgery. The incision begins at the level of the inferior border of the zygomatic arch, anterior to the tragus, and extends towards the contralateral pupillary line. A subgaleal and interfascial dissection is performed. Then, the zygomatic arch is vertically sectioned twice and mobilized downwards, together with the masseter muscle. Next, a fronto-temporo-sphenoidal craniotomy is performed and complete exposure of the anterior temporal dura achieved. Thus, the surgical possibilities are: (i) intradural access to the middle fossa; (ii) intradural pretemporal access to the basal cisterns; (iii) intradural transtemporal access to the insular region; and (iv) extradural access to the middle fossa. The transzygomatic approach offers excellent exposure to the floor of the middle fossa and the lateral wall of the cavernous sinus (both intradurally and extradurally). Also, combined with a pretemporal approach, it affords a good view of the interpeduncular cistern; and using a transtemporal approach, it provides good access to the insular region.

Experience from the Argentine Pegvisomant Observational Study: Preliminary Data

The GH receptor antagonist pegvisomant is an efficient agent to achieve biochemical control of acromegaly in those cases refractory to surgery and medical therapy with somatostatin analogs. We conducted an observational multicenter study consisting of data collection in accordance with the standard management of patients with acromegaly in everyday practice. We reviewed the medical records of 28 patients, 23 females, who were treated with pegvisomant due to the lack of biochemical response or intolerance to the somatostatin analogs. The objective was to monitor long-term safety and efficacy of the antagonist. 82% of the patients had previous pituitary surgery, 53.6% radiotherapy and 96.4% received medical therapy for acromegaly. Only 19.2% of the patients had pituitary residual tumor size larger than 1 cm, the remainder harbored a microadenoma or no visible tumor in the pituitary images. In terms of biochemical efficacy, IGF-I levels decreased to normal ranges in 45% and 58.8% of patients after 3 and 6 months of treatment, respectively, the daily mean dose of pegvisomant being 9.6+/-1.1 mg. Adverse events, potentially related to pegvisomant were reported in 6 patients (21.4%), local injection site reaction and elevated liver enzymes being the most frequent. Tumor size did not show enlargement in the evaluated population (15 patients) during the period of the study. This paper presents preliminary data from a small observational study in Argentina which represents the first database in our country.

EXPRESSION OF C-MYC AND C-FOS AND BINDING SITES FOR ESTRADIOL AND PROGESTERONE IN HUMAN PITUITARY TUMORS

We studied the concentration of mRNA from the oncogenes c-myc and c-fos in human pituitary adenomas by Northern blot hybridization (35 somatotrophinomas, 9 prolactinomas, 21 nonsecreting and 3 adrenocorticotrophinomas). The concentration of estrogens and progesterone receptors was also investigated. The levels of c-myc and c-fos mRNA was higher in nonsecreting tumors which were generally the largest and had a higher percentage of recurrence after surgery than the other groups. High concentration of estrogen receptors was observed in tumors derived from cells which are normally the target of this hormone, mainly prolactinomas. They were also present in somatotrophic and nonsecreting adenomas, related to the presence of prolactin or gonadotrophin cells in these tumors. The presence of estrogen receptors indicates that the tumor cells maintain their differentiation and a good prognosis as is the case for prolactinomas. We did not find any relationship between estrogen receptors and the concentration of c-myc and c-fos oncogenes. Larger adenomas (mainly nonsecreting) had higher levels of c-myc and c-fos mRNA than the other tumors and they had an important percentage of recurrence after surgery. It is clear that tumor size is related to the outcome after surgery and that nonsecreting adenomas are usually large because of the late diagnosis. However two large somatotrophinomas with extrasellar expansion also had overexpression of both oncogenes and both relapsed after surgery.

Exposure of the Sciatic Nerve in the Gluteal Region Without Sectioning the Gluteus Maximus: An Anatomical and Microsurgical Study

BACKGROUND Complete sectioning of the gluteus maximus muscle is an extensive procedure when approaching the sciatic nerve in the buttock, resulting in significant morbidity and a prolonged postoperative recovery period. By contrast, dissecting through the muscle by splitting its fibers is faster, involves less damage to tissues and diminishes recovery time. The objective of the present work was to perform a cadaveric study to obtain measurements of the maximum, minimum and mean exposure that this minimally invasive approach can offer. METHODS Both gluteal regions from each of ten fresh cadavers were dissected via a transgluteal approach, using a transverse curvilinear incision. After exposure of the sciatic nerve, the maximum length of exposed nerve was measured. As a final step, a 6 cm long sural graft reconstruction was performed, aided by a surgical microscope and microscopic techniques. FINDINGS The mean sciatic nerve exposure obtained was 115.4 ± 17.9 mm, ranging from a maximum of 152 mm to a minimum of 90 mm. In all 20 cases, it was possible to perform microsurgical reconstruction under the microscope. We further illustrate these findings with three live patients in whom the transgluteal approach was employed to successfully expose and repair the sciatic nerve. CONCLUSIONS The transgluteal approach is useful in the operative repair of lesions of the proximal sciatic nerve. It is a less invasive technique than classical complete sectioning of the gluteus maximus muscle, and yields better aesthetic results and a faster return to normal daily activities. Complex lesions, like nerve trauma requiring grafts and nerve tumours, can be treated with minimal risk. Nevertheless, it is less comfortable for the surgeon, and the entire extent of the exposed nerve might not be visualized simultaneously during surgery.

Bromocriptine and the expression of c-myc and c-fos in human prolactinomas.

Abstract Prolactinomas are one of the most frequent tumors of the human anterior pituitary. Dopamine agonists are the choice in the medical treatment of this disease. Bromocriptine (BC) is a well known anti-neoplasic agent in human PRL secreting adenomas although its effect on PRL cells is far from clear. We decided to investigate its influence on cell proliferation parameters: (3H)thymidine incorporation, expression of c-myc and c-fos, and number of estrogen receptors present in the samples. A total of 28 patients were included in this protocol. They were treated with BC (5-7.5 mg day-1 patient-1) or with vehicle orally 15 days before surgery. We found that in BC treated patients (3H)thymidine incorporation was lower than in vehicle treated patients. The oncogenes expression were diminished in BC comparing with vehicle-treated patients. No difference in the number of estrogen receptors was observed in the samples from BC or vehicle-treated patients. These results clearly demonstrate that one mechanism to reduce the size of human PRL secreting adenomas by BC is the inhibition of DNA duplication. [Neurol Res 2001; 23: 721-723]