Experimental Study On The Expression And Function Of PC4in Non-small Cell Lung Cancer

BackgroundLung cancer is the most leading cause of cancer-related deaths. Approximately1.6million new cases are diagnosed and nearly1.4million patients die of lung cancerworldwide each year. Non-small cell lung cancer (NSCLC) accounts for almost85%of alllung cancer cases. About40%of NSCLC are often in an advanced stage when diagnosing,and overall5-year survival rate of NSCLC patients is only10–15%. As a promisingapproach for NSCLC treatment, molecular targeted therapy has emerged and severaltargeted agents have been explored. However, there is still a need to identify new specificand efficient targeting molecules to provide multi-pathways for future NSCLC therapy.Transcriptional positive coactivator4(PC4) is a multifunctional nuclear protein that playsimportant roles in DNA transcription, replication, repair and heterochromatinization. PC4also has been recently found to show an upregulated level in several kinds of cancer. Thisprompts us to further study the significance of PC4in cancer therapy.ObjectiveIn this work, the expression of PC4in NSCLC and its possible clinical significance onthe development and progression of NSCLC have been investigated, and the function ofPC4in NSCLC has been demonstrated by in-vitro and in-vivo study. Additionally, thepotential role of PC4in the proliferation and senescence of rat bone marrow-derivedmesenchymal stem cells (MSCs) has also been studied.MethodsPC4expression in6fresh NSCLC samples was detected by RT-PCR and Western blot,and the expression of PC4in104formalin-fixed NSCLC specimens was evaluated byimmunohistochemcal staining and its semiquantitative analysis. After the downregulation ofPC4expression by sequence-specific small interfering RNA (siRNA), the proliferation, cellcycle, apoptosis and metabolism of human NSCLC cells were assayed in vitro. Human NSCLC cell xenografts in nude mice were established and treated by intratumoral injectionof Lipofectamine2000plus PC4specinfic siRNA. Silencing of PC4expression bysequence-specific siRNA in rat bone marrow-derived MSCs was also performed.ResultsIn this work, we demonstrate for the first time that PC4may represent a potentialtherapeutic target in NSCLC. PC4expression is significantly upregulated in NSCLCcarcinoma tissues compared with their adjacent non-cancerous counterparts in6freshNSCLC samples and104pairs of formalin-fixed NSCLC specimens. Knockdown of PC4expression by sequence-specific siRNA in human NSCLC cells (A549, H460and H358)significantly inhibits the growth of cancer cells by the induction of cell cycle arrest, theincrease of cell apoptosis and the reduction of cell mitochondrial energy metabolism invitro. Interrupting the PC4signaling pathway by injection of the PC4siRNA liposomecomplex produces an effective regression of pre-established A549cell xenografts in micethrough growth inhibition and increased apoptosis. Additionally, silencing of PC4expression by sequence-specific siRNA in rat bone marrow-derived MSCs significantlyinhibits the cell growth in culture and results in cellular senescence.ConclusionThe above-mentioned results indicate that PC4may represent an attractive newtherapeutic target for the treatment of NSCLC, and it participates in the regulation of theproliferation and senescence of rat bone marrow-derived MSCs.