Intensity-modulated radiotherapy alone compared with intensity-modulated radiotherapy plus concurrent chemotherapy in intermediate-risk nasopharyngeal carcinoma : A prospective multicenter phase II trial.

BACKGROUND: This study aimed to investigate the clinical benefit of adding concurrent chemotherapy to intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma (NPC) patients with an intermediate risk (stage II and T3N0M0). METHODS: A multicenter phase II randomized trial was conducted in intermediate-risk NPC patients. Enrolled patients were previously untreated and aged ranged from 18 to 70 years without severe coexisting diseases. Patients were randomly assigned to receive IMRT alone or IMRT+concurrent chemotherapy (CC; three cycles of 80 mg/m2 cisplatin every 3 weeks). Primary endpoint was defined as 3­year progression-free survival (PFS). The secondary endpoints were distant metastasis-free survival (DMFS), locoregional relapse-free survival (LRRFS), overall survival (OS), and treatment-associated toxicity. We registered this study with Chinese Clinical Trial Registry (CliCTR1800017132; registered July 13, 2018, study start July 13, 2018). RESULTS: From November 2015 to July 2019, 42 patients with stage II and T3N0M0 NPC were enrolled; 20 patients received IMRT alone while 22 patients received IMRT+CC. After a median of 58 months of follow-up, we estimated the 3­year PFS rates as 90% (IMRT group) and 86.4% (IMRT+CC group; hazard ratio 1.387, 95% confidence interval 0.240-8.014; P = 0.719). The 3­year PFS, OS, and cumulative DMFS and LRRFS showed no significant differences between the two groups (P > 0.05). However, the IMRT group displayed a lower incidence of nausea/vomiting, leucopenia, and dry mouth than the IMRT+CC group. CONCLUSION: Adding CC to IMRT provided no survival benefit but increased treatment-associated toxicities in patients with intermediate-risk NPC.

MGr1-Antigen/37 kDa laminin receptor precursor promotes cellular prion protein induced multi-drug-resistance of gastric cancer.

Cellular prion protein (PrPC), the infective agent of transmissible spongiform encephalopathies, is thought to be related to several cellular physiological and physiopathological processes. We have previously reported that PrPC participates in multi-drug-resistance of gastric cancer. As the salient ligand molecule of PrP for participating in internalization and propagation of the scrapie form of prion protein (PrPSc), 37 kDa laminin receptor precursor protein (37LRP) shared the same gene coding sequence of MGr1-Ag, another protein previously found to be involved in multi-drug-resistance of gastric cancer in our lab. In the present study, we explored whether MGr1-Ag/37LRP contributed to PrPC mediated multi-drug-resistance in gastric cancer. Immunohistochemical staining showed similar expression patterns of MGr1-Ag/37LRP and PrPC in gastric cancer tissue serial sections. Western blot and immunohistochemistry also demonstrated correlative expression of MGr1-Ag/37LRP and PrPC in gastric cancer cell lines. Interaction between MGr1-Ag/37LRP and PrPC in gastric cancer cell lines and gastric cancer tissues were verified by immunofluorescence and co-immunoprecipitation. Furthermore, knockdown of MGr1-Ag/37LRP significantly attenuated PrPC induced multi-drug-resistance by sensitizing drug-induced apoptosis through inhibition of AKT activation. In conclusion, MGr1-Ag/37LRP may interact with PrPC and promote the PrPC induced multi-drug-resistance in gastric cancer through PI3K/AKT pathway. The current study elucidates the mechanism of how PrPC triggers intracellular signaling cascade resulting in multi-drug-resistance phenotype and provides a novel candidate molecular target against gastric cancer.

The miR27b-CCNG1-P53-miR-508-5p axis regulates multidrug resistance of gastric cancer.

Multidrug resistance (MDR) correlates with treatment failure and poor prognosis among gastric cancer (GC) patients. In a previous study using high-throughput functional screening, we identified 11 microRNAs (miRNAs) that regulate MDR in GC and found that miR-508-5p reversed MDR by targeting ABCB1 and ZNRD1. However, the mechanism by which miR-508-5p was decreased in chemo-resistant GC cells was unclear. In this study, we found that ectopic miR-27b is sufficient to sensitize tumors to chemotherapy in vitro and in vivo. Moreover, miR-27b directly targets the 3' untranslated regions (3'-UTRs) of CCNG1, a well-known negative regulator of P53 stability. Interestingly, miR-27b up-regulation leads to increased miR-508-5p expression, and this phenomenon is mediated by CCNG1 and P53. Further investigation indicated that miR-508-5p is directly regulated by P53. Thus, the miR-27b/CCNG1/P53/miR-508-5p axis plays important roles in GC-associated MDR. In addition, miR-27b and miR-508-5p expression was detected in GC tissues with different chemo-sensitivities, and we found that tissues in which miR-27b and miR-508-5p are up-regulated are more sensitive to chemotherapy. Together, these data suggest that the combination of miR-27b and miR-508-5p represents a potential marker of MDR. Restoring the miR-27b and miR-508-5p levels might contribute to MDR reversion in future clinical practice.

Thioredoxin-like protein 2b facilitates colon cancer cell proliferation and inhibits apoptosis via NF-κB pathway.

Our previous work identified thioredoxin-like protein 2 (Txl-2), a novel thioredoxin family member, as the target of the monoclonal antibody MC3 which can detect colon cancer with high sensitivity and specificity. In the present study, the function of the most abundant isoform Txl-2b in cell proliferation and apoptosis was investigated. Txl-2 overexpression correlated with increased clinical stages. Inhibition of Txl-2b suppressed cell proliferation, induced cell cycle arrest at the G1/S phase, and led to responsiveness to the vincristine-induced apoptosis in SW620 cells. Txl-2b overexpression in LoVo cells had the opposite effect, which was dependent on Trx domain function. In vivo studies validated that Txl-2b expression promoted colon cancer tumorigenesis in nude mice. Further studies revealed that nuclear factor-κB (NF-κB) signaling was activated by Txl-2b. Inhibition of NF-κB activation partly abrogated the pro-proliferation and anti-apoptotic phenotypes mediated by Txl-2b via reduced Cyclin D1, Bcl-2, Bcl-xL and Survivin expression and increased Caspase-3 activation. Overall, our results indicate that Txl-2b expression stimulates cancer cell proliferation, accelerates the cell cycle and contributes to apoptosis resistance in colon cancer and provides a potential therapeutic target for colon cancer treatment.

miR-17-5p promotes proliferation by targeting SOCS6 in gastric cancer cells.

This study aimed to test the exact functions and potential mechanisms of miR-17-5p in gastric cancer. Using real-time PCR, miR-17-5p was found to be expressed more highly in gastric cancer compared with-normal tissues. Gain- and loss-of-function assays demonstrated that miR-17-5p increased the proliferation and growth of gastric cancer cells in vitro and in vivo. Through reporter gene and western blot assays, SOCS6 was shown to be a direct target of miR-17-5p, and proliferative assays confirmed that SOCS6 exerted opposing function to that of miR-17-5p in gastric cancer. In short, miR-17-5p might function as a pro-proliferative factor by repressing SOCS6 in gastric cancer.

Thioredoxin-like protein 2 is overexpressed in colon cancer and promotes cancer cell metastasis by interaction with ran.

AIMS: Our previous work identified thioredoxin-like protein 2 (Txl-2) as the target of the monoclonal antibody MC3 associated with colon cancer, but its underlying mechanisms remain poorly understood. Txl-2, a novel thioredoxin (Trx) and nucleoside diphosphate kinase family member, is alternatively spliced and gives rise to three different Txl-2 isoforms. In this study, Txl-2 expression in colon cancer, differential functions for Txl-2 isoforms in cell invasion and metastasis, and the downstream signaling were investigated. RESULTS: Txl-2 expression was elevated in colon cancer tissues compared to normal colonic tissues, with a high correlation between the histological grade and prognosis. Knockdown of Txl-2 expression significantly inhibited cancer cell motility, and the invasive and metastatic abilities of colon cancer cells. Interestingly, Txl-2 isoforms showed differential effects on cancer cell invasion and metastasis. Cell invasion and metastasis were significantly promoted by Txl-2b but inhibited by Txl-2c, while no obvious effect was observed for Txl-2a. Furthermore, a direct interaction was identified between Txl-2b and Ran, a Ras-related protein, by yeast two-hybrid assay and coimmunoprecipitation. PI3K pathway was found to be a major pathway mediating Txl-2b induced tumor invasion and metastasis. INNOVATION: The current study provides a novel biomarker and target molecule for the diagnosis and treatment of colon cancer and provides a novel paradigm to understand how alternative splicing functions in human cancer. CONCLUSION: Our findings demonstrate an elevated Txl-2 expression in colon cancer and that Txl-2b promotes cell invasion and metastasis through interaction with Ran and PI3K signaling pathway.

Factor V Leiden and inflammatory bowel disease: a systematic review and meta-analysis.

BACKGROUND: Recent studies proved that inflammatory bowel disease (IBD) patients had a higher risk of thromboembolism and a Factor V Leiden mutation that prevents the efficient inactivation of factor V, which leads to thromboembolism and thus contributes to a high potential risk of IBD. However, the relationship between Factor V Leiden mutation and IBD remains controversial. METHODS: We conducted a systematic review with meta-analysis of studies assessing the association of Factor V Leiden mutation with the risk of IBD in humans. We extracted the number of IBD and control subjects with or without Factor V Leiden mutation from each study and conducted this analysis using a fixed-effects model. RESULTS: Nineteen studies met the inclusion criteria and were included in the meta-analysis. No significant heterogeneity was found in results across the 19 studies (I (2) = 18.8%, P = 0.23), which showed a slight but not significant increase in the risk of IBD with Factor V Leiden mutation in the general population (summary odds ratio [OR] 1.13, 95% confidence interval [CI] 0.87-1.46). Taking into account ethnic differences, further study exhibited a slight but not significant increase in risk of IBD with Factor V Leiden mutation in Europeans (summary OR 1.20, 95% CI 0.88-1.64). However, Factor V Leiden mutation was significantly associated with a higher risk of thromboembolism in IBD patients (summary OR 5.30, 95% CI 2.25-12.48). No publication bias was found in this study. CONCLUSIONS: This meta-analysis indicated that although Factor V Leiden mutation was not significantly associated with the risk of IBD, it was significantly associated with a higher risk of thromboembolism in IBD patients.

Adenoviral-mediated RNA interference targeting URG11 inhibits growth of human hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is the second most common malignancy in Asia, with a 5-year survival rate of less than 5% due to high recurrence after surgery and resistance to chemotherapy. A variety of therapeutic interventions to treat HCC, particularly gene therapy, have recently been investigated in tumor model systems to provide a more complete understanding of hepatocarcinogenesis and effectively design therapeutic strategies to treat this disease. In our study, we constructed an adenoviral vector expressing small interfering RNA (siRNA) targeting a newly discovered gene named upregulated gene 11 (URG11). We introduced this vector into HCC cells to investigate the role of URG11 in HCC carcinogenesis. We observed that upon URG11 knockdown, HCC cell proliferation was inhibited through downregulation of several G1-S phase related molecules including cyclin D1 and apoptosis was induced as a result of Bcl-2 downregulation. Besides decreased expression of cyclin D1, CDK4, pRb and Bcl-2, URG11 also suppressed several other proteins including CAPN9, which was identified by cDNA microarray and 2D gel electrophoresis. Moreover, Ad-URG11-siRNA significantly suppressed HCC tumor growth in nude mice. In conclusion, Ad-URG11-siRNA can significantly suppress HCC tumor growth in vitro and in vivo by silencing the URG11 gene, and the use of this vector for gene therapy may represent a novel strategy to treat human HCC.

15-Hydroxyprostaglandin dehydrogenase is a tumor suppressor of human gastric cancer.

Cyclooxygenase-2 (COX-2), the key enzyme in prostaglandin synthesis, is often over-expressed in human gastric cancer. Recently, 15-hydroxyprostaglandin dehydrogenase [NAD+] (15-PGDH), the key enzyme in prostaglandin degradation, was found to be down-regulated in human gastric cancer tissues, but little is known about its role in gastric tumorigenesis. In this study, expression plasmids containing 15-PGDH siRNA were constructed and transfected into the gastric cancer cell line MKN45, which expresses endogenous 15-PGDH at a high level. The 15-PGDH gene was also transfected into the gastric cancer cell line SGC7901, which expresses endogenous 15-PGDH at a low level. When compared with the empty vector transfectant, MKN45 cells stably transfected with the 15-PGDH siRNA plasmid had a significantly increased proliferation rate. In contrast, SGC7901 cells stably transfected with the 15-PGDH cDNA had a significantly decreased growth rate. Furthermore, increased expression of 15-PGDH suppressed clone formation of gastric cancer cells in plate and soft agar colony formation assays in vitro and suppressed tumor formation in athymic nude mice in vivo. Stable silencing of 15-PGDH in gastric cancer cells also enhanced cell cycle entry in vitro. These results demonstrate for the first time that 15-PGDH acts as a tumor suppressor in human gastric cancer and provide further validation for 15-PGDH as a potential therapeutic target for human gastric cancer.

Decreased expression of CIAPIN1 is correlated with poor prognosis in patients with esophageal squamous cell carcinoma.

BACKGROUND: CIAPIN1, a newly identified antiapoptotic molecule, is a downstream effector of the receptor tyrosine kinase-Ras signaling pathway in the mouse Ba/F3 pro-B cell line. Neither CIAPIN1 expression nor its clinical significance has been previously examined in esophageal squamous cell carcinoma (ESCC), and the present immunohistochemical analysis is the first study on CIAPIN1 distribution in ESCC. AIMS: To investigate the relationships between the expression of CIAPIN1 and clinicopathological characteristics of ESCC, and evaluate the relationship between the expression of this gene and prognosis in ESCC patients. METHODS: The expression of CIAPIN1 was investigated in 112 surgically resected specimens of ESCC by immunohistochemistry using a specific monoclonal antibody. The relations of CIAPIN1 expression with clinicopathological characteristics and the postoperative survival rate were statistically analyzed. RESULTS: We found that the expression of CIAPIN1 was statistically correlated with the degree of differentiation, depth of invasion, and lymph node metastasis of ESCC. Consistently, the survival rates of patients with CIAPIN1-negative tumors tended to be statistically lower than those with CIAPIN1-positive tumors. However, no significant difference was observed between CIAPIN1 expression and the patient age, sex, tumor location, and distant metastasis. Furthermore, multivariate analysis was performed by using Cox's proportional hazards model, and the results showed that lymph node metastases and CIAPIN1 expression were two independent prognostic factors. CONCLUSIONS: CIAPIN1 might play an important role in esophageal carcinogenesis, and it could be considered as a valuable prognostic indicator in ESCC. Finally, functional enhancement of CIAPIN1 might lead to a novel strategy for the treatment of SCC in the esophagus.

MiR-150 promotes gastric cancer proliferation by negatively regulating the pro-apoptotic gene EGR2.

Accumulating evidence suggests small non-coding RNAs (microRNAs) play important roles in human cancer progression. In the present study, we found miR-150 was overexpressed in gastric cancer cell lines and tissues. Ectopic expression of miR-150 promoted tumorigenesis and proliferation of gastric cancer cells. Luciferase reporter assay demonstrated that EGR2 was a direct target of miR-150. Collectively, our study demonstrated that overexpression of miR-150 in gastric cancer could promote proliferation and growth of cancer cells at least partially through directly targeting the tumor-suppressor EGR2, suggesting a potential strategy for the development of miRNA-based treatment of gastric cancer.

Inhibition of the p53-MDM2 interaction by adenovirus delivery of ribosomal protein L23 stabilizes p53 and induces cell cycle arrest and apoptosis in gastric cancer.

BACKGROUND: Inhibiting MDM2 activity in tumors that express wild-type (wt) p53 but have high levels of MDM2 protein has been considered an attractive anticancer strategy for many years. Previous studies revealed that human ribosomal protein L23 (RPL23) inhibited MDM2-mediated p53 degradation and thus induced p53 levels as well as its activity, suggesting that it might be a candidate for use as a gene therapy for cancer. In the present study, we evaluated whether targeting this pathway could be of therapeutic value against human gastric carcinoma. METHODS: Gastric cancer cell lines carrying wt or mutant p53 gene were infected with adenovirus expressing RPL23 (Ad-RPL23). Cell growth assay, flow cytometry assay and morphology were used to observe the effects of Ad-RPL23 infection on tumor cells, and further, the effect of Ad-RPL23 treatment on tumor growth in vivo was investigated. RESULTS: In vitro, adenovirus-mediated RPL23 gene transfer stabilized wt p53 by inhibiting its degradation, and thus resulted in G(1)-S cell cycle arrest and/or apoptosis of human gastric cancer MKN45 and AGS cells carrying wt p53 gene. Adenovirus-mediated RPL23 gene transfer also inhibited the growth of MKN45 tumors in subcutaneous mouse models. CONCLUSIONS: The data obtained in the present study suggest that, through the inhibition of the p53-MDM2 interaction, adenovirus delivery of RPL23 can inhibit the proliferation of gastric cancer cells harboring wt p53 in vitro and in vivo. Exogenous RPL23-induced wt p53 stabilization and activation may be a novel therapeutic approach for patients with gastric cancer.

Function of PrPC (1-OPRD) in biological activities of gastric cancer cell lines.

Approximately 10-15% of the human prion disease is inherited and one of the important genetic mutations occurs in the octapeptide repeat region of prion protein gene. One of the variants, one octapeptide repeat deletion (1-OPRD), existed in several gastric cancer cell lines and its mutation frequency was higher in gastric cancer cases. However, the biological functions of it remain unknown. Wild-type and mutation forms of PrP(C) were cloned and transfected into gastric cancer cells. Cell apoptosis, adhesion, invasion, multidrug resistance (MDR) and proliferation were, respectively, investigated. Different expressed genes were screened by gene array and proved by PT-PCR. Further, luciferase report assay was used to explore the transcriptional activation of target genes. Forced overexpression PrP(C) (1-OPRD) could promote the gastric cancer cells SGC7901 growth through facilitating G1- to S-phase transition in the cell cycle. PrP(C) (1-OPRD) could also inhibit apoptosis, and promote adhesion, invasion and MDR in SGC7901. However, it exhibited no significant difference between wild-type PrP(C) (1-OPRD) and PrP(C) on apoptosis, invasion or MDR effects. Further experiments indicated that PrP(C) (1-OPRD) could trigger the transactivation of cyclinD3 besides cyclinD1 to promote cell transition and proliferation. Overexpression of PrP(C) (1-OPRD) might promote the proliferation of gastric cancer cells at least partially through transcriptional activation of cyclinD3 to accelerate the G1-/S-phase transition. The promoting proliferation effect of PrP(C) (1-OPRD) was more than that of wild-type PrP(C). However, they showed no difference on apoptosis, adhesion, invasion or MDR effects of gastric cancer cells.

Inhibition of PI3K/Akt partially leads to the inhibition of PrP(C)-induced drug resistance in gastric cancer cells.

Cellular prion protein (PrP(C)), a glycosyl-phosphatidylinositol-anchored membrane protein with unclear physiological function, was previous found to be upregulated in adriamycin (ADR)-resistant gastric carcinoma cell line SGC7901/ADR compared to its parental cell line SGC7901. Overexpression of PrP(C) in gastric cancer has certain effects on drug accumulation through upregulation of P-glycoprotein (P-gp), which is suggested to play an important role in determining the sensitivity of tumor cells to chemotherapy and is linked to activation of the phosphatidylinositol-3-kinase/Akt (PI3K/Akt) pathway. In the present study, we further investigate the role of the PI3K/Akt pathway in PrP(C)-induced multidrug-resistance (MDR) in gastric cancer. Immunohistochemistry and confocal microscope detection suggest a positive correlation between PrP(C) and phosphorylated Akt (p-Akt) expression in gastric cancer. Using established stable PrP(C) transfectant cell lines, we demonstrated that the level of p-Akt was increased in PrP(C)-transfected cells. Inhibition of PrP(C) expression by RNA interference resulted in decreased p-Akt expression. Inhibition of the PI3K/Akt pathway by one of its specific inhibitors, LY294002, or by Akt small interfering RNA (siRNA) resulted in decreased multidrug resistance of SGC7901 cells, partly through downregulation of P-gp induced by PrP(C). Taken together, our results suggest that PrP(C)-induced MDR in gastric cancer is associated with activation of the PI3K/Akt pathway. Inhibition of PI3K/Akt by LY2940002 or Akt siRNA leads to inhibition of PrP(C)-induced drug resistance and P-gp upregulation in gastric cancer cells, indicating a possible novel mechanism by which PrP(C) regulates gastric cancer cell survival.

RhoE enhances multidrug resistance of gastric cancer cells by suppressing Bax.

We have previously reported that RhoE is overexpressed in the SGC7901/VCR cell line. However, the potential role of RhoE in the development of multidrug resistance of gastric cancer is unknown. In the present study, RhoE enhanced the resistance of SGC7901 cells to several kinds of antitumor drugs. RhoE overexpression did not alter the intracellular adriamycin accumulation of SGC7901 cells nor the expression of P-gp and MRP-1, but protected SGC7901 cells from vincristine-induced apoptosis. RhoE was found to downregulate the expression of Bax at a posttranscriptional level. Western blot revealed no effects of RhoE on the activities of the Caspase family of proteins. In brief, our study demonstrated that RhoE may promote the multidrug resistance phenotype of gastric cancer cells by decreasing the expression of Bax at posttranscriptional level, thus inhibiting vincristine-induced apoptosis.

Effect of a novel inhibitory mAb against beta-subunit of F1F0 ATPase on HCC.

Hepatocellular carcinoma (HCC) represents a worldwide health problem. F1F0 ATPase, one of the most unique supermolecule enzymes in the inner mitochondrial membrane, was recently found located also on the plasma membrane of some tumor and epithelial cells. Ecto-F1F0 ATPase might play the major role in maintaining the normal average intracellular pH in those cells relative to tumor acidic extracellular microenviroment. Inhibiting the extracellular F1F0 ATPase on tumor exhibits both antiangiogenic and antitumorigenic activities. We found previously a strain of murine mAb, mAb6F2C4, which binds with beta-catalytic subunit of F1F0 ATPase. Immunofluorescence and flow cytometry assay showed that mAb6F2C4 could bind with plasma membrane of diverse hepatoma cells and HUVEC. Moreover, it could markedly block extracellular ATP generation of SMMC-7721 cells under extracellular acidic condition. In vitro, mAb6F2C4 retarded not only the proliferation and colony forming ability of SMMC-7721 cells, but also the proliferation and tube formation ability of HUVEC. mAb6F2C4 was located on plasma membrane of some hepatoma cells and attenuated dramaticly tumor growth in tumor xenograft models in nude mice. Therefore, we concluded that mAb6F2C4 binding with ecto-beta-subunit of F1F0 ATPase, could inhibit extracellular ATP synthesis and exhibit both antiangiogenic and antitumorigenic activities, which could be further developed for HCC therapy.

Proteasome inhibitor MG132 reverses multidrug resistance of gastric cancer through enhancing apoptosis and inhibiting P-gp.

Multidrug resistance (MDR) is a major impediment to the effective chemotherapy of many human malignancies. Although much effort has been devoted to develop new drugs for overcoming MDR, until now, still no useful method of reversing MDR, suitable for clinical use, has emerged from this large quantity of work. Some researchers have reported that proteasome inhibitors could induce apoptosis in a variety of cancer cells. In the present study, we found that, in vincristine-resistant human gastric cancer cell line SGC7901/VCR, proteasome inhibitor MG132 was an effective inducer of apoptosis, and also had the capacity of downregulating the expression of anti-apoptotic Bcl-2 and MDR1 (P-gp), by which MG132 resensitized tumor cells to the apoptosis induced by anticancer drugs. Data presented by drug sensitivity assay further demonstrated that MG132 could reverse the resistant phenotype of gastric cancer cells effectively through both enhancing drug-induced apoptosis and inhibiting P-gp. The further study of the effectiveness and safety of proteasome inhibitor in vivo may be helpful for developing a new possible strategy to treat gastric cancer MDR.

A new apoptosis inhibitor, CIAPIN1 (cytokine-induced apoptosis inhibitor 1), mediates multidrug resistance in leukemia cells by regulating MDR-1, Bcl-2, and Bax.

We investigated the role of cytokine-induced apoptosis inhibitor 1 (CIAPIN1), a newly identified apoptosis inhibitor, in leukemia cell multidrug resistance (MDR) and its possible underlying mechanisms. CIAPIN1 was found to be overexpressed at the mRNA and protein levels in the vincristine-induced multidrug-resistant leukemia cell line HL-60/VCR, compared with HL-60, its parental cell line. In this study, we transfected HL-60 with a eukaryotic expression vector of CIAPIN1. In vitro drug sensitivity assays suggested that HL-60-CIAPIN1 cells conferred resistance to both P-glycoprotein (P-gp)-related and -unrelated drugs. Blocking CIAPIN1 expression in HL-60/VCR cells by CIAPIN1-specific small interfering RNA increased the cells' sensitivity to various chemotherapeutic drugs. Flow cytometry results suggested that CIAPIN1 expression could suppress adriamycin-induced apoptosis, accompanied by a decreased accumulation and increased release of adriamycin. Semiquantitative RT-PCR, Western blot analysis, and luciferase reporter assays suggested that CIAPIN1 could significantly upregulate the expression of MDR-1 and Bcl-2, the transcription of the MDR-1 gene, as well as downregulate the expression of Bax. Additionally, the inhibition of CIAPIN1 expression by RNA interference or P-gp inhibitor could partially reverse CIAPIN1-mediated MDR. Taken together, our findings suggest that downregulating CIAPIN1 could sensitize leukemia cells to chemotherapeutic drugs by downregulating MDR-1 and Bcl-2 and by upregulating Bax, yet not altering either glutathione-S-transferase activity or intracellular glutathione content in leukemia cells. Further study of CIAPIN1's function may reveal more of the mechanisms of leukemia MDR and result in the development of strategies to treat leukemia.

Differential expression of calcium-related genes in gastric cancer cells transfected with cellular prion protein.

The prion protein (PrPC) has a primary role in the pathogenesis of transmissible spongiform encephalopathies, which causes prion disorders partially due to Ca2+ dysregulation. In our previous work, we found that overexpressed PrPC in gastric cancer was involved in apoptosis, cell proliferation, and metastasis of gastric cancer. To better understand how PrPC acts in gastric cancer, a human microarray was performed to select differentially regulated genes that correlate with the biological function of PrPC. The microarray data were analyzed and revealed 3798 genes whose expression increased at least 2-fold in gastric cancer cells transfected with PrPC. These genes encode proteins involved in several aspects of cell biology, among which, we specially detected molecules related to calcium, especially the S100 calcium-binding proteins, and found that PrPC upregulates S100A1, S100A6, S100B, and S100P but downregulates CacyBP in gastric cancer cells. We also found that intracellular Ca2+ levels in cells transfected with PrPC increased, whereas these levels decreased in knockdowns of these cells. Taken together, PrPC might increase intracellular Ca2+, partially through calcium-binding proteins, or PrPC might upregulate the expression of S100 proteins, partially through stimulating the intracellular calcium level in gastric cancer. Though the underlying mechanisms need further exploration, this study provides a new insight into the role of PrPC in gastric cancer and enriches our knowledge of prion protein.

Hypoxia induced overexpression of PrP(C) in gastric cancer cell lines.

Cellular prion protein (PrP(C)), a copper-binding glycosyl-phosphatidylinositol (GPI)-anchored membrane protein that is expressed predominantly in neurons can be induced in ischemia/hypoxic brain tissues. It was also found to be overexpressed and conferred multidrug resistance, promoting cancer metastasis and inhibiting apoptosis in gastric cancer in our lab. In solid tumors, hypoxia can promote malignant progression and confer resistance to chemotherapy by altering gene expression. In present study, we investigated the molecular mechanisms and signaling pathway involved in the induction of the PrP(C) gene by hypoxia in cancer cell lines. PrP(C) was detected to be upregulated in several cancer cell lines at both mRNA and protein level, and then found to be induced by hypoxia in a time-dependent manner. After hypoxia treatment, gastric cancer MKN28 cells transfected with luciferase reporter constructs of the human PrP(C) promoter, which contained HSE, expressed higher luciferase activities (4.3-fold) than those cells transfected with the constructs containing no HSE. In addition, the upregulation of PrP(C) was reduced by MERK/ERK inhibitor (PD98059). siRNA knockdown of PrP(C) could make the cells more sensitive to hypoxia induced drug sensitivity. In conclusion, from these findings, we can propose that some transcriptional factors phosphorylated by ERK1/2, could in turn interact with HSE in the promoter of PrP(C) resulting in upregulation of PrP(C) in gastric cancer cell line MKN28 during hypoxia. Downregulation of PrP(C) makes gastric cancer cells more sensitive to hypoxia induced drug sensitivity. However, other mechanisms might also be responsible for hypoxia induced overexpression of PrP(C) in gastric cancer.