Expression And Distribution Of Aquaporin 1 And Auaporin 4 In Laryngeal Carcinoma And Its Significance

Background:Aquaporins (AQPs) are a family of water-selectivetransporting glycoproteins that have a wide increase plasmamembrane water permeability in secretory and adsorptive cells, andin those cells which the rapid regulated water movement is required.Water transport occurs across plasma membranes in all cells forhousekeeping functions such as volume regulation and etc. Thechange of expression and function of AQPs has effect not only onthe transport of water but also on the vital activity. The recentdiscovery has drawn attention to their roles in physiologicalprocess and several human diseases involving rapid water transportand have identified them as potential targets for therapeuticintervention. Most tumors have been shown to exhibit highvascular permeability and high interstitial fluid pressure, itsneonatal blood vessel possesses high permeability to plasmaproteins and macromolecular substances , and may have animportant effect on growth, invasion and metastasis of carcinoma.Potential importance of AQP1 in oncology and carcinogenesishas only recently been recognized. The AQP1 gene may play apotentially important role in cell proliferation since it has beenshown to be a delayed early-response gene involved in cellcycle control. However, only a limited amount of information isavailable concerning the distribution of AQPs in pathologicallyaltered tissues, and the transport pathways for water within tumorsremain unknown. Studying this mechanism could help usunderstanding more about the progression of tumor growth,invasion and metastasis.Objective:To detect expression level and distribution ofaquaporin 1(AQP1) and aquaporin 4 (AQP4)in laryngealcarcinoma and try to find out the significance of AQP1 and AQP4in the invasion of laryngeal carcinoma.Method:1. Eight cases of laryngeal tissues were obtainedfrom normal wistar rats. The slides were detected byimmunohistochemical staining for observing the expression ofAQP1 and AQP4 in mammalian laryngeal tissue.2. Twenty cases of laryngeal carcinoma tissues and fifteencases of normal tissues beside tumors were acquired immediatelyafter surgery. The expression and distribution of AQP1 and AQP4in laryngeal carcinoma were examined by reverse transcriptasepolymerase chain reaction , western blot analysis andimmunohistochemical technique.Result: 1. Both AQP1 and AQP4 expressed on laryngealtissues of wistar rats. AQP1 expressed mainly on the capillaryendothelia of laryngeal mucous lamina propria, laryngeal mucousglands and myocyte nuclear membrane. AQP4 expressed mainly onsquamous epithelial, pseudostratified ciliated columnar epithelia,laryngeal mucous glands and myocyte membrane. The distributionof Aquaporin 1 and aquaporin 4 on rat laryngeal tissue isdramatically different.2. Both AQP1 and AQP4 expressed on human laryngealcarcinoma tissues and normal laryngeal tissues.Reverse Transcriptase-Polymerase Chain ReactionAQP1 and AQP4 mRNA were expressed in laryngealcarcinoma and normal laryngeal tissues. AQP1 mRNAexpression level in laryngeal tumor tissues is remarkablystronger compared with that in normal tissues beside tumors(t=2.591,P<0.05). There is no difference of AQP4 mRNAbetween laryngeal tumor tissues and normal laryngeal tissues(t=1.796, P>0.05).Western Blot AnalysisAQP1 expression is dramatically increased in the laryngealcarcinoma tissues over the normal laryngeal tissue beside tumor(t=2.612,P>0.05).there is no difference between laryngealtumor tissues and normal laryngeal tissues(t=1.939,P>0.05).Immunohistochemical FingdingsThe AQP1 water channel expressed in all of the tumors andnormal tissues. But the distribution is dramatically differentbetween laryngeal carcinoma and normal laryngeal tissues. Theexpression of AQP1 in laryngeal carcinoma was located mainly onthe capillary endothelia cells, tumor cells themselves and cancernests. However, the expression of AQP1 in normal laryngeal tissuewas located on the capillary endothelia of laryngeal mucous laminapropria and laryngeal mucous glands. A semiquantitativeassessment of the distribution of AQP1 showed that expressionlevel in laryngeal tumor tissues is remarkably stronger comparedwith normal tissues beside tumors (t=2.939, P<0.01).AQP4 expressed mainly on squamous epithelial,pseudostratified ciliated columnar epithelia and laryngeal mucousglands of normal laryngeal tissues, and expressed on tumor cellmembrane and cancer nests of laryngeal carcinoma tissues. Asemiquantitative assessment of the distribution of AQP4 showedthat expression level in laryngeal tumor tissues is not different tothat in normal tissues beside tumors(t=1.577,P>0.05).Discussion: Invasion and metastasis of tumor is a highselective process. This process is related with the tumor trait andthe surrounding environment of tumor tissue. Water is the majorcomponent of all human cells and tissues. Water metabolism playsan important role in this course. To satisfy the fast proliferation,splitting, invasion and metastases, malignant tumors have activelymetabolism, and tumor cells need more water to transport themembrane than normal cells. So aquaporins are very important tosurvival of tumor cells and tumor tissues. Recent studies haveapproved that many tumor tissues, cell lines and capillaryendothelia of macrangium expressed aquaporins high. AQPs maybe responsible for the high vascular permeability and interstitialfluid pressure in tumors. AQPs may also play a role in tumorangiogenesis and may be involved in development of effusions oredema fluid.Though AQP1 and AQP4 all have function to transport water,but the distribution and expression of them in laryngeal tissue, andthe function in microenvironment are different. This studyapproved that the expression of AQP1 in normal laryngeal tissuewas located on the capillary endothelia of laryngeal mucous laminapropria and laryngeal mucous glands but not on epithelia. This cantransport water fast through capillary endothelia cells to satisfy theneed of laryngeal cells and has an important role in keeping thenormal laryngeal function. AQP4 expressed mainly on squamousepithelial, pseudostratified ciliated columnar epithelia andlaryngeal mucous glands of normal laryngeal tissues but not on thecapillary endothelia. This is very important to excrete laryngealmucus and keep humidity of respiratory tract.This study has shown that a great deal of AQP1 expressed onthe capillary endothelia cells and immature neonatal blood vesselof tumor, AQP1 mRNA and protein expression level in laryngealtumor tissues are remarkably stronger compared with normaltissues beside tumors. Our result suggested that overexpression ofAQP1 contributed to the hyperpermeability of tumor vessels inlaryngeal carcinoma tissues. The AQP1 synthesis can increase thehydrostatic interstitial pressure which may cause hypoxia, hypoxiathen can accelerate angiogenesis of laryngeal carcinoma. Thisstudy has also shown that AQP1 expressed in tumor cells andcancer nests of laryngeal carcinoma tissues. This result suggestedthat AQP1 may increase the permeability of tumor cell membrane,influence the volume and composition of the liquid layer oflaryngeal carcinoma cells, thus stimulate the tumor growth andinvasion. This study also confirmed that AQP4 expressed mainlyon tumor cell membrane and cancer nests of laryngeal carcinomatissues. The distribution of AQP1 and AQP4 on laryngealcarcinoma tissues is dramatically different. They may increasewater osmotic transport cooperatively in tumor epithelium andvessels, and thus promote the development and the metastasis oftumors.The expression and distribution of kinds of AQPs on laryngealcarcinoma can ensure tumor cells to get more water with lessenergy and accelerate invasion and metastasis progression oftumors. But the detailed mechanism of it should be studied incontinued works.Conclusion:This study confirmed first time that both AQP1and AQP4 expressed on laryngeal carcinoma tissues and normallaryngeal tissues, but the distribution of AQP1 and AQP4 onlaryngeal carcinoma tissues was dramatically different , andAQP1 expression level in laryngeal tumor tissues was remarkablystronger than that in normal tissues beside tumors. Inhibition of theexpression of AQP1 may suppress the process of the tumorinvasion and metastases.