Effects Of Hypoxia In Tumor Tissue To Invasive Of Pituitary Adenomas

Background Pituitary adenomas were the most common benign tumor in skull base,however,there was about 40%-70%similarly to malignant among them in biological characters.We now still have no more knowledge about it.Hypoxia,a condition of oxygen deprivation,is a common feature of many forms of solid tumors.It emerges when the stromal vascular system fails to deliver a sufficient amount of oxygen to the growing tumor.As a result,many tumors under adaptive genetic changes that allow them to avoid hypoxia-induced cell death and necrosis.In recent years, considerable research effort has focus on the feature of the tumors.Many events that occur during the adaptation of a tumor to hypoxia are mediated through a group of hypoxia inducible factor-1(HIF-1).HIF-1 is a heterodimeric transcription factor,consisting of an oxygen sensitive HIF-1αsubunit and a constitutively present HIF-1βsubunit,also known as aryl hydrocarbon nuclear translocator(ARNT).Clinical and experimental evidencehas now accrued highlighting intratumoral hypoxia as the main locomotive driving tumor induced angiogenesis and devastated of ECMs,and HIF-1 regulates the invasive and matastasis of the most tumors.However,few researches now provide the effects of HIF-1 in pituitary adenomas.Among the various HIF-1 dependent genes,vascular endothelial growth factor(VEGF)and matrix metalloproteinase-2(MMP-2)figure prominently as the main effector in matching vascular supply to the metabolist and metastasis needs of the tumors,acting as both a potent angiogenesis molecule and as a survival factor for newly formed vessels. Though there were lots of studies that HIF-1 is the main regulator of VEGF and MMP-2 in tumor,no investigation provides the correlations of HIF-1 with VEGF and MMP-2 in pituitary adenomas.To our knowledge,this research is the first in the literature to evaluate the role of HIF-1 as a regulator of VEGF and MMP-2 expression in pituitary adenomas.Chapter 1.The expression of HIF-1αin pituitary adenomas and relationship with invasion of pituitary adenomasObject To explore mRNA and protein expressions of hypoxia inducible factor 1α(HIF-1α)in invasive and non-invasive pituitary adenomas,analyse the correlation of protein expression HIF-1αwith the grade and volume of pituitary adenomas.Methods The expression of HIF-1αwas determined by reverse transcription polymerase chain reaction(RT-PCR),the immunostaining and western blotting for protein expression of HIF-1αin total 42 patients divided into invasive and non-invasive pituitary adenomas groups and in 5 normal sham patients.The difference of HIF-1αmRNA and protein expression between different groups was compared,and the correlation of protein expression HIF-1αwith the invasion,grade and volume of pituitary adenomas were analysed by the method of Spearman's correlation coefficient.Result The protein expression of HIF-1αin invasive pituitary adenomas group were significantly higher than non-nvasive pituitary adenomas group(x~2=9.147,P＜0.01),while the protein expression of HIF-1αin pituitary adenomas group were significantly higher than sham group(x~2=16.31,P＜0.01).There were no significant different of HIF-1αmRNA expression between invasive and non-invasive pituitacy adenomas groups(t=1.041,P＞0.05).The protein expression of HIF-1αin gradeⅢandⅣwere significantly higher than gradeⅠandⅡof pituitary adenomas groups(x~2=5.56,P＜0.05).furthermore.The protein expression of HIF-1αwas higher in diameter beyond 30mm of pituitary adenomas groups.The correlation of anslyses showed there were a positive relation of HIF-1αprotein expression and the size of pituitary adenomas(r=0.397,P＜0.01).Conclusion There was overexpression of HIF-1αprotein in pituitary adenomas,and the HIF-1αprotein is regulated by translational and posttranslational mechanism in hypoxia.These studies suggest the hypothetical mechanism that the activation of HIF-1αprotein increases the invasion of pituitary adenomas.Chapter 2.The relationship between HIF-1αand VEGF expression with invasion of pituitary adenomasObjective To examine mRNA and protein expressions of the HIF-1αand vascular endothelial growth factor(VEGF)in pituitary adenomas.The protein expression and correlation between HIF-1αand VEGF in invasive and non-invasive pituitary adenomas were analysed. The purpose was to explore the relationship between these proteins and angiogenesis and invasion in pituitary a denomas.Methods 42 patients were divided into invasive and non-invasive pituitary adenomas groups.The mRNA expressions of the HIF-1αand VEGF were determined by RT-PCR,and the protein expression of HIF-1αand VEGF were measured by immunostaining in pituitary adenomas samples.Furthermore,we surveyed the microvessel density (MVD)by FⅧfactor.The differences of HIF-1αand VEGF mRNA expression between different groups were compared by Pearson's correlation coefficient and the protein expression by Spearman's correlation coefficient.We analysed the relationship between VEGF and MVD by Spearman's correlation coefficient.Results The protein expressions of HIF-1αand VEGF in invasive pituitary adenomas group were significantly higher than non-nvasive pituitary adenomas group(x~2=9.147,P＜0.01 and x~2=5.401,P＜0.05). There were significant different of VEGF mRNA expression between invasive and non-invasive pituitary adenomas groups(t=2.416,P＜0.05) and no significant different of HIF-1αmRNA expression(t=1.041,P＞0.05).The correlated analyses of mRNA and protein expression showed there was a negative relation between HIF-1αand VEGF in non-invasive pituitary adenomas groups(P＞0.05),and a positive relation in invasive pituitary adenomas groups(r=0.890,P＜0.05 and r=0.436,.P＜0.05).There was a positive relation between VEGF and MVD(r=0.785,P＜0.01).Conclusion There was highly expression of HIF-1αand VEGF mRNA in invasive pituitary adenomas at the same time.The overexpression of HIF-1αand VEGF protein leads to the angiogenesis of pituitary adenomas,especially in invasive pituitary adenomas.HIF-1αmay have an important regulating role in VEGF protein expression in invasiveness of pituitary adenomas.We conclude that the hypoxia/ HIF-1α/VEGF pathway may play important role of angiogenesis and the increasing invasiveness of pituitary adenomas.Chapter 3.The relationship between HIF-1αand MMP-2 expression with invasion of pituitary adenomasObjective To study mRNA and protein expressions of the HIF-1αand Matrix metalIoproteinase-2(MMP-2)in pituitary adenomas.The protein expression and correlation between HIF-1αand MMP-2 in invasive and non-invasive pituitary adenomas were analysed.The purpose was to explore the relationship between these proteins and invasion of pituitary adenomas.Method 42 patients were divided into invasive and non-invasive pituitary adenomas groups.The mRNA expressions of the HIF-1αand MMP-2 were determined by RT-PCR,and the protein expression of HIF-1αand MMP-2 were measured by immunostaining in pituitary adenomas samples.Furthermore,we surveyed the microvessel density (MVD)by FⅧfactor.The differences of HIF-1αand MMP-2 mRNA expression between different groups were compared by Pearson's correlation coefficient and the protein expression by Spearman's correlation coefficient.We analysed the relationship between MMP-2 and MVD by Spearman's correlation coefficient.Result The protein expressions of HIF-1αand MMP-2 in invasive pituitary adenomas group were significantly higher than non-nvasive pituitary adenomas group(x~2=9.147,P＜0.01 and x~2=4.75,P＜0.05).There were significant different of MMP-2 mRNA expression between invasive and non-invasive pituitary adenomas groups(t=0.757,P＜0.01)and no significant different of HIF-1αmRNA expression(t=1.041,P＞0.05).The correlated analyses of mRNA expression showed there was a negative relationship between HIF-1αand MMP-2 in invasive and non-invasive pituitary adenomas groups(P＞0.05),while the protein expression have positive relationship(r=0.866,P＜0.01 and r=0.478,P＜0.05).There was a positive relation between MMP-2 and MVD(r=0.611,P＜0.05).Conclusion There was higher expression of HIF-1αand MMP-2 mRNA and protein in invasive pituitary adenomas at the same time than non-invasive pituitary adenomas.The overexpression of MMP-2mRNA and protein is related to the invasiveness of pituitary adenomas by breaking down extracellular matrix(ECM).HIF-1αmay have an important promoting role in MMP-2 protein expression in pituitary adenomas.We conclude that the hypoxia/HIF-1α/MMP-2 pathway may play important role of breaking down ECM and increasing invasiveness of pituitary adenomas.