Cancerous inhibitor of protein phosphatase 2A enhances chemoresistance of gastric cancer cells to oxaliplatin

BACKGROUND Cancerous inhibitor of protein phosphatase 2A(CIP2A)is a newly discovered oncogene.It is an active cell proliferation regulatory factor that inhibits tumor apoptosis in gastric cancer(GC)cells.CIP2A is functionally related to chemoresistance in various types of tumors according to recent studies.The underlying mechanism,however,is unknown.Further,the primary treatment regimen for GC is oxaliplatin-based chemotherapy.Nonetheless,it often fails due to chemoresistance of GC cells to oxaliplatin.AIM The goal of this study was to examine CIP2A expression and its association with oxaliplatin resistance in human GC cells.METHODS Immunohistochemistry was used to examine CIP2A expression in GC tissues and adjacent normal tissues.CIP2A expression in GC cell lines was reduced using small interfering RNA.After confirming the silencing efficiency,3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide tetrazolium and flow cytometry assays were used to evaluate cell proliferation and apoptosis caused by oxaliplatin treatment.Further,the key genes and protein changes were verified using realtime quantitative reverse transcription PCR and Western blotting,respectively,before and after intervention.For bioinformatics analysis,we used the R software and Bioconductor project.For statistical analysis,we used GraphPad Prism 6.0 and the Statistical Package for the Social Sciences software version 20.0(IBM,Armonk,United States).RESULTS A high level of CIP2A expression was associated with tumor size,T stage,lymph node metastasis,Tumor Node Metastasis stage,and a poor prognosis.Further,CIP2A expression was higher in GC cells than in normal human gastric epithelial cells.Using small interfering RNA against CIP2A,we discovered that CIP2A knockdown inhibited cell proliferation and significantly increased GC cell sensitivity to oxaliplatin.Moreover,CIP2A knockdown enhanced oxaliplatin-induced apoptosis in GC cells.Hence,high CIP2A levels in GC may be a factor in chemoresistance to oxaliplatin.In human GC cells,CIP2A regulated protein kinase B phosphorylation,and chemical inhibition of the protein kinase B signaling pathway was significantly associated with increased sensitivity to oxaliplatin.Therefore,the protein kinase B signaling pathway was correlated with CIP2Aenhanced chemoresistance of human GC cells to oxaliplatin.CONCLUSION CIP2A expression could be a novel therapeutic strategy for chemoresistance in GC.

Protein tyrosine phosphatase non-receptor Ⅱ:A possible biomarker of poor prognosis and mediator of immune evasion in hepatocellular carcinoma

BACKGROUND The incidence of primary liver cancer is increasing year by year.In 2022 alone,more than 900000 people were diagnosed with liver cancer worldwide,with hepatocellular carcinoma(HCC)accounting for 75%-85%of cases.HCC is the most common primary liver cancer.China has the highest incidence and mortality rate of HCC in the world,and it is one of the malignant tumors that seriously threaten the health of Chinese people.The onset of liver cancer is occult,the early cases lack typical clinical symptoms,and most of the patients are already in the middle and late stage when diagnosed.Therefore,it is very important to find new markers for the early detection and diagnosis of liver cancer,improve the therapeutic effect,and improve the prognosis of patients.Protein tyrosine phosphatase non-receptor 2(PTPN2)has been shown to be associated with colorectal cancer,triple-negative breast cancer,non-small cell lung cancer,and prostate cancer,but its biological role and function in tumors remain to be further studied.AIM To combine the results of relevant data obtained from The Cancer Genome Atlas(TCGA)to provide the first in-depth analysis of the biological role of PTPN2 in HCC.METHODS The expression of PTPN2 in HCC was first analyzed based on the TCGA database,and the findings were then verified by immunohistochemical staining,quantitative real-time polymerase chain reaction(qRT-PCR),and immunoblotting.The value of PTPN2 in predicting the survival of patients with HCC was assessed by analyzing the relationship between PTPN2 expression in HCC tissues and clinicopathological features.Finally,the potential of PTPN2 affecting immune escape of liver cancer was evaluated by tumor immune dysfunction and exclusion and immunohistochemical staining.RESULTS The results of immunohistochemical staining,qRT-PCR,and immunoblotting in combination with TCGA database analysis showed that PTPN2 was highly expressed and associated with a poor prognosis in HCC patients.Kyoto Encyclopedia of Genes and Genomes enrichment analysis showed that PTPN2 was associated with various pathways,including cancer-related pathways,the Notch signaling pathway,and the MAPK signaling pathway.Gene Set Enrichment Analysis showed that PTPN2 was highly expressed in various immune-related pathways,such as the epithelial mesenchymal transition process.A risk model score based on PTPN2 showed that immune escape was significantly enhanced in the high-risk group compared with the low-risk group.CONCLUSION This study investigated PTPN2 from multiple biological perspectives,revealing that PTPN2 can function as a biomarker of poor prognosis and mediate immune evasion in HCC.

Molecular Docking Studies of Botanical Beverage Mix Berries (LIFEGREENTM) against Breast Cancer Cells from Targeted Protein 1QQG, 7B5Q & 7B5O & Uterine Fibroid from Targeted Protein 2AYR, 6T41 & 3GRF

Fibroids, also called leiomyomas or myomas, are communal tumors of the muscle or uterine wall that affect about 20% of females who are of reproductive age. They can look as if singly or in clusters, and they often cease to grow after menopause. Fibroids can be classified as intramural, sub serosal, pedunculated, or submucosal based on where they are positioned in the uterus. Although fibroids are benign, they can grow quickly and cause a range of symptoms, such as pelvic pressure, heavy menstrual flow, and infertility. As a result, fibroids are a main reason behind hysterectomy surgeries. The majority of cases of breast cancer are ductal and lobular cancers, making it the second utmost common cancer in women international. Gene mutations like those in BRCA1 or BRCA2 knowingly raise the risk of breast and other cancers, typically with an earlier cancer onset. Cancer risk is influenced by a complex interplay of genetic abnormalities, environmental factors, and lifestyle selections. Further research into these relations is domineering. Although they are common in uterine leiomyomas, especially multiple leiomyomas, MED12 mutations do not significantly correlate with tumor size. These mutations have also been noticed in smooth muscle tumors and leiomyosarcomas, two other types of uterine cancer. The identification of MED12 mutations as the sole genetic abnormality originates in leiomyomas raises the opportunity of a role in the genesis of cancer. 10% - 15% of women who are of reproductive age have endometriosis, which grants serious difficulties because of its chronic nature and range of clinical symptoms. Even after effective surgeries, issues reoccur often, adding to the enormous financial burden. The effects of MED12 mutations have been experiential in recent studies examining the molecular causes of endometriosis-associated infertility, which have shown anomalies in cellular connections and signaling cascades. Computational techniques were used in this study to investigate LifeGreenTM’s potential to prevent uterine fibroids and breast cancer. The efficacy of LifeGreenTM as a preventive measure or a treatment for common gynecological matters was examined and modeled. We investigated the mechanisms underlying LifeGreenTM’s benefits in the treatment of uterine fibroids and breast cancer using computational techniques. Our research contributes to our understanding of its potential therapeutic benefits for women’s health.

Neural Wiskott-Aldrich syndrome protein(N-WASP)promotes distant metastasis in pancreatic ductal adenocarcinoma via activation of LOXL2

Pancreatic ductal adenocarcinoma(PDAC)is one of the most aggressive solid malignancies.A specific mechanism of its metastasis has not been established.In this study,we investigated whether Neural Wiskott-Aldrich syndrome protein(N-WASP)plays a role in distant metastasis of PDAC.We found that N-WASP is markedly expressed in clinical patients with PDAC.Clinical analysis showed a notably more distant metastatic pattern in the N-WASP-high group compared to the N-WASP-low group.N-WASP was noted to be a novel mediator of epithelialmesenchymal transition(EMT)via gene expression profile studies.Knockdown of N-WASP in pancreatic cancer cells significantly inhibited cell invasion,migration,and EMT.We also observed positive association of lysyl oxidase-like 2(LOXL2)and focal adhesion kinase(FAK)with the N-WASP-mediated response,wherein EMT and invadopodia function were modulated.Both N-WASP and LOXL2 depletion significantly reduced the incidence of liver and lung metastatic lesions in orthotopic mouse models of pancreatic cancer.These results elucidate a novel role for N-WASP signaling associated with LOXL2 in EMT and invadopodia function,with respect to regulation of intercellular communication in tumor cells for promoting pancreatic cancer metastasis.These findings may aid in the development of therapeutic strategies against pancreatic cancer.

Overexpression of mitogen-activated protein kinase phosphatase-1 in endothelial cells reduces blood-brain barrier injury in a mouse model of ischemic stroke

Ischemic stroke can cause blood-brain barrier(BBB)injury,which worsens brain damage induced by stroke.Abnormal expression of tight junction proteins in endothelial cells(ECs)can increase intracellular space and BBB leakage.Selective inhibition of mitogen-activated protein kinase,the negative regulatory substrate of mitogen-activated protein kinase phosphatase(MKP)-1,improves tight junction protein function in ECs,and genetic deletion of MKP-1 aggravates ischemic brain injury.However,whether the latter affects BBB integrity,and the cell type-specific mechanism underlying this process,remain unclear.In this study,we established an adult male mouse model of ischemic stroke by occluding the middle cerebral artery for 60 minutes and overexpressed MKP-1 in ECs on the injured side via lentiviral transfection before stroke.We found that overexpression of MKP-1 in ECs reduced infarct volume,reduced the level of inflammatory factors interleukin-1β,interleukin-6,and chemokine C-C motif ligand-2,inhibited vascular injury,and promoted the recovery of sensorimotor and memory/cognitive function.Overexpression of MKP-1 in ECs also inhibited the activation of cerebral ischemia-induced extracellular signal-regulated kinase(ERK)1/2 and the downregulation of occludin expression.Finally,to investigate the mechanism by which MKP-1 exerted these functions in ECs,we established an ischemic stroke model in vitro by depriving the primary endothelial cell of oxygen and glucose,and pharmacologically inhibited the activity of MKP-1 and ERK1/2.Our findings suggest that MKP-1 inhibition aggravates oxygen and glucose deprivation-induced cell death,cell monolayer leakage,and downregulation of occludin expression,and that inhibiting ERK1/2 can reverse these effects.In addition,co-inhibition of MKP-1 and ERK1/2 exhibited similar effects to inhibition of ERK1/2.These findings suggest that overexpression of MKP-1 in ECs can prevent ischemia-induced occludin downregulation and cell death via deactivating ERK1/2,thereby protecting the integrity of BBB,alleviating brain injury,and improving post-stroke prognosis.

Uncoupling protein 2 deficiency of non-cancerous tissues inhibits the progression of pancreatic cancer in mice

Background: Pancreatic ductal adenocarcinoma(PDAC) is a disease of the elderly mostly because its development from preneoplastic lesions depends on the accumulation of gene mutations and epigenetic alterations over time. How aging of non-cancerous tissues of the host affects tumor progression, however, remains largely unknown. Methods: We took advantage of a model of accelerated aging, uncoupling protein 2-deficient( Ucp2 knockout, Ucp2 KO) mice, to investigate the growth of orthotopically transplanted Ucp2 wild-type(WT) PDAC cells(cell lines Panc02 and 6606PDA) in vivo and to study strain-dependent differences of the PDAC microenvironment. Results: Measurements of tumor weights and quantification of proliferating cells indicated a significant growth advantage of Panc02 and 6606PDA cells in WT mice compared to Ucp2 KO mice. In tumors in the knockout strain, higher levels of interferon-γ m RNA despite similar numbers of tumor-infiltrating T cells were observed. 6606PDA cells triggered a stronger stromal reaction in Ucp2 KO mice than in WT animals. Accordingly, pancreatic stellate cells from Ucp2 KO mice proliferated at a higher rate than cells of the WT strain when they were incubated with conditioned media from PDAC cells. Conclusions: Ucp2 modulates PDAC microenvironment in a way that favors tumor progression and implicates an altered stromal response as one of the underlying mechanisms.

Protein Phosphatase 2A as a Drug Target in the Treatment of Cancer and Alzheimer's Disease

Protein phosphatase 2A(PP2A)is a major serine/threonine phosphatase which participates in the regulation of multiple cellular processes.As a confirmed tumor suppressor,PP2A activity is downregulated in tumors and its re-activation can induce apoptosis of cancer cells.In the brains of Alzheimer's disease(AD)patients,decreased PP2A activity also plays a key role in promoting tau hyperphosphorylation and A0 generation.In this review,we discussed compounds aiming at modulating PP2A activity in the treatment of cancer or AD.The upstream factors that inactivate PP2A in diseases have not been fully elucidated and further studies are needed.It will help for the refinement and development of novel and clinically tractable PP2A-targeted compounds or therapies for the treatment of tumor and AD.

The expression and localization of a novel protein phosphatase inhibitor 2810408A11Rik in mouse testis and sperm

This study investigated the expression and distribution of 2810408A11Rik in mouse testis and sperm, and explored its role in sperrnatogenesis and sperm function. The expression levels of 2810408A11Rik mRNA in multiple tissue samples were analyzed using bioinformatic resources and RT-PCR technique. A specific rabbit polyclonal antibody was prepared by prokaryotic expression of 2810408A11Rik recombinant protein and utilized for animal immunization. Western blotting, immunohistochemistry and immunofluorescence were used to detect the expression and distribution of 2810408A11Rik. The results of the bioinformatic analysi and RT-PCR showed that 2810408A11Rik mRNA was specifically expressed in mouse testis, and 2810408AllRik protein included a protein phosphatase inhibitor domain. Western blotting assays, immunohistochemistry and immunofluorescence confirmed the expression of 2810408A11Rik protein in mouse testis, especially in post-meiosis round and long spermatids, and that it is localized in the acrosome and the post-nucleus area of sperm. Our findings suggest that 2810408A11Rik may play an important role in spermatogenesis, sperm capacitation and fertilization.

Use of programmed cell death protein ligand 1 assay to predict the outcomes of non-small cell lung cancer patients treated with immune checkpoint inhibitors

The recent discovery of immune checkpoints inhibitors, especially anti-programmed cell death protein 1(PD-1)and anti-programmed cell death protein ligand 1(PD-L1) monoclonal antibodies, has opened new scenarios in the management of non-small cell lung cancer(NSCLC) and this new class of drugs has achieved a rapid development in the treatment of this disease. However, considering the costs of these drugs and the fact that only a subset of patients experience long-term disease control, the identification of predictive biomarkers for the selection of candidates suitable for treatment has become a priority. The research focused mainly on the expression of the PD-L1 receptor on both tumor cells and/or immune infiltrates determined by immunohistochemistry(IHC). However, different checkpoint inhibitors were tested, different IHC assays were used, different targets were considered(tumor cells, immune infiltrates or both) and different expression thresholds were employed in clinical trials. In some trials the assay was used prospectively to select the patients, while in other trials it was evaluated retrospectively. Some confusion emerges, which makes it difficult to easily compare the literature data and to translate them in practice management. This mini-review shows the possibilities and pitfalls of the PD-L1 expression to predict the activity and efficacy of anti PD1/PD-L1 monoclonal antibodies in the treatment of NSCLC.

Discovery of a small-molecule bromodomain-containing protein 4 inhibitor that induces AMP-activated protein kinase-modulated autophagy-associated cell death in breast cancer

OBJECTIVE To discover a small-molecule bromodomain-containing protein 4(BRD4)inhibitor that induces AMP-activated protein kinase-modulated autophagy-associated cell death in breast cancer and exploreits potential mechanisms.METHODS BRD4 interactors were analyzed by PPI network prediction and The Cancer Genome Atlas(TCGA)analysis.The interaction between BRD4 and AMPK was confirmed by co-immunoprecipitation assay.Novel BRD4 inhibitors were designed and synthesized based upon pharmacophore analysis of BRD4(1),then screened by antiproliferative activity and Alpha Screen of BRD4(1).The selectivity of the best candidate compound 8f was validated by co-crystallization,FRET assay and co-immuno precipitation assay.The mechanisms of 8f were investigated by fluorescence microscopy,electron microscopy,Western blotting,immunocytochemistry,si RNA and GFP-m RFP-LC3 plasmid transfections,as well as immunohistochemistry and immunofluorescence.Potential mechanisms were discovered by i TRAQ-based proteomics analysis and the therapeutic effect of 8f was assessed by xenograft breast cancer mouse and zebrafish models.RESULTS We identified that BRD4 interacted with AMPK,which was remarkably downregulated in breast cancer.We next designed and synthesized 49 candidate compounds,and eventually discovered a selective small-molecule inhibitor of BRD4(8f).Subsequently,8f was discovered to induce autophagyassociated cell death(ACD)by BRD4-AMPK interaction,and thus activating AMPK-m TOR-ULK1-modulated autophagic pathway in breast cancer cells.Interestingly,the i TRAQ-based proteomics analyses revealed that 8f induced ACD pathways,involved in HMGB1,VDAC1/2 and e EF2.Moreover,8f displayed a therapeutic potential on both xenograft breast cancer mouse and zebrafish models.CONCLUSION We discovered a novel small-molecule inhibitor of BRD4 that induces BRD4-AMPK-modulated ACD in breast cancer,which may provide a candidate drug for future cancer therapy.

SMAC exhibits anti-tumor effects in ECA109 cells by regulating expression of inhibitor of apoptosis protein family

BACKGROUND The poor prognosis and rising incidence of esophageal cancer highlight the need for improved therapeutics that are essential prior to treatment.LCL161 is an SMAC(second mitochondrial activator of caspases)mimic and inhibitor of apoptosis protein(IAP)antagonist which exhibits anti-tumor effects and improves the chemical sensitivity of many cancers.AIM To ascertain the effects and mechanisms of the SMAC analog LCL161 on esophageal cancer cells.METHODS MTT assay and TUNEL assay were used to detect cell proliferation and apoptosis,respectively.Western blot analysis was used to study the molecular mechanisms of LCL161-induced death of ECA109 cells.RESULTS LCL161 decreased ECA109 cell proliferation in dose-and time-dependent manner and induced apoptosis of ECA109 cells in a dose-dependent manner.Also,LCL161 induced a significant decrease in the expression of the XIAP and significant increase in the expression of Caspase-3.In addition,Bax increased significantly with increasing concentrations of LCL161,and the relative expression of Bax was significantly different between groups.CONCLUSION These findings support the hypothesis that LCL161 can inhibit proliferation and induce apoptosis in esophageal cancer cells by regulating the expression of IAP family members,suggesting that it has potential to be an effective treatment for esophageal squamous cell carcinoma.

Structural Insight into the Design on Oleanolic Acid Derivatives as Potent Protein Tyrosine Phosphatase 1B Inhibitors

Oleanolic acid derivatives act as newer protein tyrosine phosphatase 1B （PTP-1B） inhibitors for type 2 diabetes mellitus （T2DM）. In order to understand the structural requirement of PTP-1B inhibitors, 52 oleanolic acid derivatives were divided into a training set （34 compounds） and a test set （18 compounds）. The highly reliable and predictive 3D-QSAR models were constructed by CoMFA, CoMSIA and topomer CoMFA methods, respectively. The results showed that the cross validated coefficient （q2） and non-cross-validated coefficient （R2） were 0.554 and 0.999 in the CoMFA model, 0.675 and 0.971 in the CoMSIA model, and 0.628 and 0.939 in the topomer CoMFA model, which suggests that three models are robust and have good exterior predictive capabilities. Furthermore, ten novel inhibitors with much higher inhibitory potency were designed. Our design strategy was that （i） the electronegative substituents （Cl, -CH2OH, OH and -CH2Cl） were introduced into the double bond of ring C, （ii） the hydrogen bond acceptor groups （C≡N and N atom）, electronegative groups （C≡N, N atom, -COOH and -COOCH3） and bulky substituents （C6H5N） were connected to the C-3 position, which would result in generating potent and selective PTP-1B inhibitors. We expect that the results in this paper have the potential to facilitate the process of design and to develop new potent PTP-1B inhibitors.

Human antigen R mediated post-transcriptional regulation of inhibitors of apoptosis proteins in pancreatic cancer

AIM To determine the association of human antigen R(HuR) and inhibitors of apoptosis proteins(IAP1, IAP2) and prognosis in pancreatic cancer.METHODS Protein and mRNA expression levels of IAP1, IAP2 and HuR in pancreatic ductal adenocarcinoma(PDAC) were compared with normal pancreatic tissue. The correlations among IAP1/IAP2 and HuR as well as their respective correlations with clinicopathological parameters were analyzed. The Kaplan-Meier method and log-rank tests were used for survival analysis. Immunoprecipitation assay was performed to demonstrate HuR binding to IAP1, IAP2 mRNA. PANC1 cells were transfected with either anti-HuR siRNA or control siRNA for 72 h and quantitative reverse transcription polymerase chain reaction(RT-PCR), western blot analysis was carried out.RESULTS RT-PCR analysis revealed that HuR, IAP1, IAP2 mRNA expression were accordingly 3.3-fold, 5.5-fold and 8.4 higher in the PDAC when compared to normal pancreas(P < 0.05). Expression of IAP1 was positively strongly correlated with HuR expression(P < 0.05, r = 0.783). Western blot analysis confirmed RTPCR results. High IAP1 expression, tumor resection status, T stage, lymph-node metastases, tumor differentiation grade, perineural and lymphatic invasion were identified as significant factors for shorter survival in PDAC patients(P < 0.05).Immunohistological analysis showed that HuR was mainly expressed in the ductal cancer cell's nucleus and less so in cytoplasm. RNA immunoprecipitation analysis confirmed IAP1 and IAP2 post-transcriptional regulation by HuR protein. Following siHuR transfection, IAP1 mRNA and protein levels were decreased, however IAP2 expression levels were increased.CONCLUSION HuR mediated overexpression of IAP1 significantly correlates with poor outcomes and early progression of pancreatic cancer. Further studies are needed to assess the underlying mechanisms.

High expression of protein phosphatase 2 regulatory subunit B''alpha predicts poor outcome in hepatocellular carcinoma patients after liver transplantation

BACKGROUND Protein phosphatase 2 regulatory subunit B''alpha(PPP2R3A)gene has been reported in other tumors,but the influence of PPP2R3A gene expression on the occurrence,development,and prognosis of hepatocellular carcinoma(HCC)remains unclear.AIM To investigate whether the PPP2R3A gene could be used to predict tumor recurrence and survival of HCC patients after liver transplantation(LT).METHODS Diseased liver tissues of HCC patients after LT were collected as well as their clinical data and follow-up information.The immunohistochemical method was used to detect the expression of PPP2R3A protein in the tissues of 108 patients with primary liver cancer.Theχ2 test was used to analyze the relationship between PPP2R3A protein expression levels and the clinicopathological features of tumors.The Kaplan-Meier method was used to analyze overall postoperative survival.The COX proportional hazard model was used to analyze adverse prognostic factors.RESULTS Immunohistochemistry showed that the PPP2R3A protein was mainly expressed in the cytoplasm of HCC cells.Compared to corresponding peritumoral tissues,expression was higher in HCC tissues(P≤0.001).Correlation analysis showed that high PPP2R3A expression was correlated with preoperative serum alphafetoprotein(AFP)levels(P=0.003),tumor-node-metastasis-t stage(P≤0.001),and envelope invasion(P=0.001).Univariate analysis showed that overall survival(P≤0.001)and recurrence-free survival(P=0.025)of patients with high PPP2R3A expression(≥4 points)were poor compared to those with low expression(<4 points).The overall survival rates or recurrence-free survival rates at 1,2,and 3 years with high PPP2R3A expression were 73%,38%,and 23%or 31%,23%,and 23%,respectively.Multivariate analysis showed that high PPP2R3A expression(hazard ratio=2.900,95%confidence interval:1.411–5.960,P=0.004)was an independent survival risk factor of HCC patients after LT,and it was also an independent predictor of postoperative tumor recurrence.This study also showed in patients with AFP≥400 ng/mL,the overall survival(P≤0.001)and recurrencefree survival(P=0.023)of those with high PPP2R3A expression were significantly worse compared to those with low PPP2R3A expression.When PPP2R3A expression was low,the overall survival rate(P=0.461)or recurrence-free survival rate(P=0.072)after LT in patients with AFP<400 ng/mL and≥400 ng/mL was not significantly difference.The 1,2,and 3 year survival rate of patients with low PPP2R3A expression and AFP<400 ng/mL were 98%,80%,and 69%,respectively,while patients who met Hangzhou criteria had a posttransplant 1,2,and 3 years overall survival rate of 89%,66%,and 55%,respectively.CONCLUSION High expression of PPP2R3A might be a potential marker for predicting poor prognosis of HCC after LT.Combined with serum AFP levels,PPP2R3A might enhance the accuracy of predicting HCC outcome in patients after LT and supplement the efficacy of the Hangzhou criteria.

Regulatory Effects of X-linked Inhibitor of Apoptosis Protein and Pro-apoptotic Protein Smac on Apoptosis Resistance to Chemotherapy in Pancreatic Cancer Cells~*

Objective： To investigate the relation of X-linked inhibitor of apoptosis （XIAP） and second mitochondria-derived activator of caspase （Smac） signaling pathway to chemoresistance in human pancreatic cancer Panc-1 and BXPC-3 cells. Methods： Apoptosis and the changes of XIAP expression in permeabilized cells induced by cisplatin and 5-fluorouracil （FU） were measured by flow cytometry. The cytosolic expression of XIAP, Smac and caspase-3 was detected by Western blot. A recombinant plasmid vector pEGFP-N1/Smac was constructed and transfected into of Pancol cells. The effect of cytosolic overexpression of Smac on apoptosis of Panc-1 cells was evaluated by flow cytometry. Results： Panc-1 was more resistant to cisplatin or 5-FU induced apoptosis than BXPC-3. Western blot revealed that chemoresistant Panc-1 highly expressed XIAP, and increased cytosolic expression of Smac might be responsible for the marked down-regulation of XIAP in chemo-sensitive BXPC-3 cells after exposure to cisplatin or 5-FU. Furthermore, cytosolic overexpression of Smac could significantly down-regulate the levels of XIAP and promote the activity of caspase-3, as well as sensitize Panc-1 cells to anticancer drug-induced apoptosis. Conclusion： Anticancer drug-induced apoptosis requires mitochondrial release of Smac and downregulation of XIAP, which may be an important determinant of chemo-sensitivity in pancreatic cancer cells. Up-regulation of cytosolic expression of Smac may act as an effective modifying signal to overcome apoptosis resistance to chemotherapy in pancreatic cancer cells.

Targeting X-linked inhibitor of apoptosis protein inhibits pancreatic cancer cell growth through p-Akt depletion

AIM: To determine whether lentivirus-mediated shRNA targeting the X-linked inhibitor of apoptosis protein (XIAP) gene could be exploited in the treatment of pancreatic cancer. METHODS: Human pancreatic cancer cells Panc-1, Mia-paca2, Bxpc-3 and SW1990, infected with lentivirus, were analyzed by real-time polymerase chain reaction (PCR). Western blotting was used to examine XIAP protein levels, survivin and p-Akt to confirm the result of real-time PCR and determine the possible mechanism. The 3-(4,5-cimethylthiazol-2-yl)-2,5- diphenyl tetrazolium bromide (MTT) assay was used to measure IC50 to determine chemosensitivity to the chemotherapeutic drugs 5-fluorouracil (5-FU) and gemcitabine. A colony assay, MTT assay and a tumorigenicity experiment were used to study cell proliferation in vitro and in vivo . Caspase-3/7 activity, 4',6-diamidino-2-phenylindole-staining and flow cytometric measurements were used to study apoptosis in SW1990 cells. RESULTS: XIAP proteins were found to be differen- tially expressed among pancreatic cancer cell lines Panc-1, Mia-paca2, Bxpc-3 and SW1990. Data of real-time PCR and Western blotting showed that XIAP was reduced persistently and markedly by lentivirus-mediated shRNA. Downregulation of XIAP by transfection with XIAP shRNA resulted in decreased p-Akt expression. XIAP shRNA also inhibited the growth of pancreatic cancer cells in vitro and in vivo , enhanced drug-induced apoptosis and increased chemosensitivity to 5-FU and gemcitabine. Results also suggest that inhibition of XIAP and subsequent p-Akt depletion may have an anti-tumor effect through attenuating the ability of cancer cells to survive. CONCLUSION: Lentivirus-mediated gene therapy is an attractive strategy in the treatment of pancreatic cancer and justifies the use of lentivirus in pancreatic cancer gene therapy studies.

The Heat Shock Protein Story—From Taking mTORC1,2 and Heat Shock Protein Inhibitors as Therapeutic Measures for Treating Cancers to Development of Cancer Vaccines

Heat shock proteins (HSPs) serve to correct proteins’ conformation, send the damaged proteins for degradation (quality control function). Heat shock factors (HSFs) are their transcription factors. The protein complexes mTOR1 and 2 (with the same core mTOR), the phosphoinositide-dependent protein kinase-1 (PDK1), the seine/threonine-specific protein kinase (Akt), HSF1, plus their associated proteins form a network participating in protein synthesis, bio-energy generation, signaling for apoptosis with the help of HSPs. A cancer cell synthesizes proteins at fast rate and needs more HSPs to work on quality control. Shutting down this network would lead to cell death. Thus inhibitors of mTOR (mTORI) and inhibitors of HSPs (HSPI) could drive cancer cell to apoptosis—a “passive approach”. On the other hand, HSPs form complexes with polypeptides characteristic of the cancer cells;on excretion from the cell, they becomes antigens for the immunity cells, eventually leading to maturation of the cytotoxic T cells, forming the basic principle of preparing cancer-specific, person-specific vaccine. Recent finding shows that HSP70 can penetrate cancer cell and expel its analog to extracellular region, giving the hope to prepare a non-person-specific vaccine covering a variety of cancers. Activation of anti-cancer immunity is the “active approach”. On the other hand, mild hyperthermia, with increase of intracellular HSPs, has been found to activate the immunity response, and demonstrate anti-cancer effects. There are certain “mysteries” behind the mechanisms of the active and passive approaches. We analyze the mechanisms involved and provide explanations to some mysteries. We also suggest future research to improve our understanding of these two approaches, in which HSPs play many roles.

Expression and Characterization of Catalytic Domain of T Cell Protein Tyrosine Phosphatase(ΔTC-PTP)——Immunohistochemical Study of ΔTC-PTP Expression in Non-small Cell Lung Carcinomas

This study objective was to express and characterize the catalytic domain of the human T cell protein tyrosine phosphatase（△TC-PTP） and to study immunohistochemically the expression of △TC-PTP in human non-small cell lung cancers. △TC-PTP gene was PCR amplified with the cDNA of human TC-PTP as template, and cloned into the pT7 expression vector. The recombinant pT7-△TC-PTP was expressed in E. coli Rosetta （ DE3 ） host cells and puri- fied. The enzymatic characteristics of △TC-PTP including enzyme activity and kinetics assay were measured. The antiserum was prepared by immunizing rabbit with the purified recombinant △TC-PTP. Rabbit polyclonal antibody against △TC-PTP was purified by PVDF immobilized antigen affinity chromatography. Immunohistochemical staining of lung cancer tissues was performed with antibody against △TC-PTP protein. △TC-PTP gene was correctly cloned, expressed, and purified. The recombinant △TC-PTP had a highly catalytic activity of PTPase. Squamous cell lung carcinoma showed a significantly higher expression rate of △TC-PTP （76. 92%, 10/13 ） than adenocarcinoma （57.14%, 4/7） and normal lung tissue（20%, 1/5 ）. This study represents the first demonstration that △TC-PTP is highly expressed in human squamous cell lung carcinomas. In addition, this study provides an important basis for further studying the biological function of TC-PTP and its relationship with lung carcinomas and other diseases.

Regulation of Ikaros function by casein kinase 2 and protein phosphatase 1

The Ikaros gene encodes a zinc finger,DNA-binding protein that regulates gene transcription and chromatin remodeling.Ikaros is a master regulator of hematopoiesis and an established tumor suppressor.Moderate alteration of Ikaros activity (e.g.haploinsufficiency) appears to be sufficient to promote malignant transformation in human hematopoietic cells.This raises questions about the mechanisms that normally regulate Ikaros function and the potential of these mechanisms to contribute to the development of leukemia.The focus of this review is the regulation of Ikaros function by phosphorylation/dephosphorylation.Site-specific phosphorylation of Ikaros by casein kinase 2 (CK2) controls Ikaros DNA-binding ability and subcellular localization.As a consequence,the ability of Ikaros to regulate cell cycle progression,chromatin remodeling,target gene expression,and thymocyte differentiation are controlled by CK2.In addition,hyperphosphorylation of Ikaros by CK2 leads to decreased Ikaros levels due to ubiquitinmediated degradation.Dephosphorylation of Ikaros by protein phosphatase 1 (PP1) acts in opposition to CK2 to increase Ikaros stability and restore Ikaros DNA binding ability and pericentromeric localization.Thus,the CK2 and PP1 pathways act in concert to regulate Ikaros activity in hematopoiesis and as a tumor suppressor.This highlights the importance of these signal transduction pathways as potential mediators of leukemogenesis via their role in regulating the activities of Ikaros.

Response of Subcutaneous Xenografts of Endometrial Cancer in Nude Mice to Inhibitors of Phosphatidylinositol 3-Kinase/Akt and Mitogen-Activated Protein Kinase (MAPK) Pathways: An Effective Therapeutic Strategy for Endometrial Cancer

Objective: This study was designed to explore whether inhibition of the extracellular-regulated kinase (ERK) and phosphatidylinositol-3-kinase (PI3K) signaling pathways can inhibit the growth of xenografts of endometrial cancer cell lines with different estrogen receptors (ER) profiles in vivo and to provide preliminary laboratory basis for the probability of endometrial adenocarcinoma treatment with blockage of the two pathways, especially to endometrial cancer with low ER status. Methods: Human endometrial cancer Ishikawa bearing ER and HEC-1Awith low ER status cells were subcutaneously injected into BALB/c nude mice to establish endometrial cancer xenograft tumor models. The effects of PI3K/Akt inhibitor LY294002, MAPK/ERK1/2 inhibitor PD-98059 and their combinations on the growth of the xenograft tumors and apoptotic state of Ishikawa and HEC-1Acells were tested in vivo using the inhibitory rate, the terminal deoxynucleotidyl transferase-mediated nick-end labeling assay, H/E-stain. Western blot analysis was used to detect the alterations of activated ERK (P-ERK) and AKT (P-AKT) during this process. Results: LY294002, a PI3K/Akt pathway inhibitor, induced significant suppression in the growth of both Ishikawa and HEC-1Acell xenograft tumors, concomitant with increased apoptosis in xenografts as evidenced by TUNEL. A similar effect was also observed when the MAPK/ERK1/2 signaling pathway was inhibited by PD98059. Concurrent inhibition of the PI3K/Akt and MAPK/ERK1/2 pathways showed enhanced anti-tumor effects in vivo as indicated by increased apoptosis. At the same time, the levels of P-ERK and P-AKT in both xenograft tumors decreased, and their levels in combination group was the lowest. Conclusions: PD98059, LY294002 and their combinations showed remarkable inhibitory effects on xenograft tumors of endometrial carcinoma cell lines with different expression status of ER in vivo through blockage of PI3K/Akt and MAPK/ERK1/2 signaling pathways. This suggests that targeting these pathways may be an effective therapeutic strategy against endometrial carcinomas, especially for ER-negative cancers which show poor response to endocrinal therapy.