Characterization Of LncRNA Gas5Expression And Its Regulatory Mechanism In Pancreatic Ductal Adenocarcinoma

Objective Pancreatic Ductal Adenocarcinoma（PDAC) is one of thefrequently reported malignancies worldwide. Recently, this disease has beenassociated with an incremental incidence. Although the life-technology andclinical practice have been significantly improved for treating the cancerpatients, the5-year survival of PDAC patients is still less than6%. Lack ofa early diagnostic marker of PDAC, after detection, this melignancyprogresses and shows metastasis in a short period which dose not allow theclinicians to control the PDAC outcome with currently utilized therapies.Thus it is required to improve the diagnostic manner and uncover theeffective treatment for the PDAC patients. Long non-coding RNAs (lncRNAs)have been reported to play a regulatory role in cancer development. It is ofinterest to understand the function of lncRNAs associated with PDAC development and uncover their potential utilization in future diagnosis andtreatment. It has been reported that lncRNA Gas5is involved in breast cancercell growth, however, the expression level and regulatory role of Gas5arestill unknown in PDAC. Hense, in this thesis, the expression of Gas5associated with PDAC progression is investigated, and the regulatorymechanism of this lncRNA has been extensively studied. The goal of thisthesis is to uncover and validate the potential utilization of Gas5in PDACdiagnosis and treatment.Methods23PDAC tumour tissues and10normal panctratic tissueswere collected. Expression of Gas5in tumour and normal tissues wasanalyzed by real-time PCR (RT-PCR). Then the correlation of Gas5expression and patients’ pathological features was analyzed. Furthermore, theexpression level of Gas5in four different PDAC cell lines (BxPC-3, PANC-1,AsPC-1and Hs766T) was quantified by RT-PCR. Based on the expression ofGas5in PDAC cells, siRNA knockdown and overexpression techniques wereused to manupulate Gas5expression and observe its function in vitro.Moreover, the possible downstream molecules regulated by Gas5signalingwas analyzed by RT-PCR and western blot after alterating Gas5expressionin the PDAC cell lines.Results The expression of Gas5is significantly reduced by about5 folds in PDAC tumour tissues when compared to normal tissues (P<0.01).The expression level of Gas5is closely associated with tumour size and TMNstage, but not related to patients’ age and sex, lymph node metastasis, tumourdifferentiation and tumour location. Also, Gas5expression is statisticallylower in four PDAC cell lines than the normal pancreatic ductal epithelialcell (P＜0.01). Overexpression of Gas5in PANC-1and BxPC3significantlyreduces the cell growth. In contrast, Gas5inhibition significantly induces asignificant decrease in G0/G1phase and an increase in S phase. Furthermore,it is uncovered that CDK6expression is regulated by Gas5and, CDK6downregulation is able to partially eliminate the outcome of Gas5inhibition.Conclusions The expression of Gas5is significantly reduced in PDACtissues when compared to normal pancreatic tissues. The reduced expressionlevel of Gas5in PDAC is associated with aggressive tumour invasion andmetastasis, which suggests that Gas5may play a role in tumour suppressionand this molecule could be used as a new prognostic marker in clinicalpractice. In addition, Gas5is involved in PDAC cell proliferation and itsfunction is partially regulated by CDK6. Thus Gas5and CDK6signalingpathway need be further studied for elustrating their potential functioninvolved in PDAC treatment. This thesis demonstrates the regulation oflncRNA associated with PDAC development, and provides new insights of trageting lncRNA in cancer therapies.