Clinical And Invasiveness-related Gene Study Of Invasive Pituitary Adenoma

ObjectivesPituitary adenoma is one of the most common intracranial tumors and accounts for 20%of primary brain tumor.The standard transsphenoidal approach has been successfully employed to resect most pituitary adenomas and provides good prognoses. As a result of parasellar or retrosellar extension,invasive pituitary adenoma can cause serious clinical symptom.Due to limited exposure of standard procedure,complete surgical removal of pituitary adenoma remains problematic.Moreover,invasive pituitary adenoma has unique biological behaviour and its pathogenesis is still unclear.These lead to poor clinical results and tumor recurrence in the long period.Therefore,efficient diagnosis and treatment strategy for invasive pituitary adenoma is based on clinical and invasiveness-related gene study.By additional bony removal of the cranial base,the extended transsphenoidal approach provides better exposure to parasellar and clival region as compared with the standard approach.E-cadherin is a kind of cell adhesion molecule and relate to tumor invasiveness.However,the relationship between E-cadherin and invasiveness in pituitary adenoma is still unclear.Bmi-1 and PIK3CA are oncogene.Bmi-1 and PIK3CA regulate cancer-related functions such as cell proliferation,invasion and apoptosis and play important role in the progression of malignant tumor.The relationship between invasive pituitary adenoma and Bmi-1 or PIK3CA has not been reported.The aim of this study is as follows.1) to describe the surgical experience using the extended transsphenoidal approach to remove pituitary adenomas invading the anterior cranial base,cavernous sinus and clivus;2) to explore the relationship between expression of E-cadherin and invasiveness in pituitary adenomas and its clinical significance;3) to investigate expression of Bmi-1 and PIK3CA in invasive pituitary adenoma and their relation to tumor invasion.Materials and Methods1) Retrospective analysis was performed in 126 patients with pituitary adenomas, surgically treated through the extended transsphenoidal approach in Peking Union Medical College Hospital from September 1999 to March 2008.2) According to modified Hardy's classification and Knosp's classification,11 specimens of pituitary adenomas were gathered and separated into invasive and noninvasive groups in this study.E-cadherin expression in two groups was analyzed by immunohistochemistry and reverse transcription-polymerase chain reaction,respectively. Meanwhile,E-cadherin expression and the invasiveness of primary cells of invasive group before and after 5-Aza-2'-deoxycytidine treatment were evaluated by immunohistochemistry and Boyden Chamber,respectively.3) Tumor invasiveness was defined with modified Hardy's classification and on the basis of pathological evidence of bony or submucosal invasion.The patients were separated into invasive and noninvasive groups in this study.The expression of Bmi-1 mRNA and PIK3CA mRNA was analyzed by real-time PCR in 19 fresh frozen tissue samples,respectively.The expression of Bmi-1 protein and PIK3CA protein was evaluated by immunohistochemistry in 2 normal pituitary tissues and 60 formalin-fixed and paraffin-embedded pituitary adenoma samples,respectively.Moreover,the expression of P53 protein and Ki-67 labeling index was assessed by immunohistochemistry in 60 formalin-fixed and paraffin-embedded pituitary adenoma samples,respectively.The results of real-time PCR and immunohistochemistry was analyzed by SPSS 13.0 software.Results1) There were 55 males and 71 females with a mean age of 43.4 years(12-75 years). There were 82 cases of macroadenoma and 44 cases of giant adenoma.The tumor extended into the anterior cranial base in 14 patients and extended laterally and encased the cavernous sinus in 111 cases,of which there were 3 patients with the pituitary adenoma extension into inferior temporal lobe,28 patients with the tumor extension posteriorly into the clivus,47 patients with the tumor extension into sphenoidal sinus via the sellar floor.Moreover,invasive tumor growth in a multidirectional manner was observed in 59 patients.Gross total resection was achieved in 78 patients(61.9%), subtotal in 43(34.1%) and partial in 5(4.0%).Postoperative complications included transient cerebrospinal rhinorrhea(7 cases),incomplete cranial nerve palsy(5), panhypopituitarism(5),internal carotid artery injury(2),monocular blindness(2), permanent diabetes insipidus(1),and perforation of nasal septum(2).No intraoperative or postoperative death was observed.2) Immunohistochemical and RT-PCR analyses revealed that expression of E-cadherin mRNA and E-cadherin protein were significantly reduced in invasive group (P<0.05).5-Aza-2'-deoxycytidine could increase expression of E-cadherin protein(P< 0.01) and somewhat inhibit the aggressiveness in primary cells of invasive pituitary adenomas(P<0.01).3) Expression of Bmi-1 mRNA and PIK3CA mRNA was significantly lower in noninvasive than in invasive group(P=0.020,P=0.013,respectively).There is negative expression of Bmi-1 protein and PIK3CA protein in normal anterior pituitary tissues. Expression of Bmi-1 protein and PIK3CA protein was significantly lower in noninvasive than in invasive group,respectively(P<0.001,P=0.005,respectively).Multivariate analysis revealed that the expression of Bmi-1 protein was a significant and prognostic parameter(P=0.007)for pituitary adenoma patients.Conclusions1) The extended transsphenoidal approach provides excellent exposure to pituitary adenomas invading the anterior cranial base,cavernous sinus and clivus.This approach enhances the degree of tumor resection while postoperative complications are relatively low.However,radical resection of the tumors that are tenacious,highly invasive to the cavernous sinus or invading multidirectionally remain a big challenge.This reasonable procedure not only allows better visualization of the tumor and the neurovascular structures but also provides significant working space under microscope,which facilitate intraoperative manipulation.Preoperative imaging study and new techniques,such as the neuronavigation system and the endoscope,improve efficacy and safety of tumor resection.2) Downregulation of E-cadherin expression is correlated with invasive pituitary adenomas and may caused by promoter hypermethylation.5-Aza-2'-deoxycytidine can improve E-cadherin expression through reversing methylation and reduce cell aggressiveness.The results may provide new information for diagnosis and treatment strategy of invasive pituitary adenoma.3) The results suggest that Bmi-1 and PIK3CA play a role in pituitary adenoma pathogenesis and relate to tumor invasiveness.These findings may provide new diagnosis and treatment strategy for invasive pituitary adenoma.Expression of Bmi-1 protein can assess the prognosis of pituitary adenoma patients and may become a novel biomarker in invasive pituitary adenoma.