STAT3 regulates 5-Fu resistance in human colorectal cancer cells by promoting Mcl-1–dependent cytoprotective autophagy

Chemoresistance to 5-fluorouracil (5-Fu)-based chemotherapy is one of the primary reasons for the failure of colorectal cancer (CRC) management. STAT3 can mediate tumor drug resistance through a variety of diverse mechanisms. Nonetheless, the underlying mechanisms of STAT3-induced 5-Fu resistance in CRC are still poorly understood. Here, we aimed to investigate the potential mechanism(s) of STAT3-induced 5-Fu resistance in CRC. Quantitative RT-PCR and Western blot were used to test the expression of STAT3 and Mcl-1 in chemosensitive and chemoresistant CRC tissues and cell lines. After overexpression or knockdown of STAT3 or Mcl-1, and/or treatment with or without 5-Fu or chloroquine (CQ), we tested cell viability, inhibitory concentration 50% (IC₅₀) value of 5-FU, cell apoptosis, proliferation, migration, and autophagy. STAT3 and Mcl-1 were significantly upregulated in the chemoresistant CRC tissues and cell lines, and STAT3 positively regulated Mcl-1. Functional studies demonstrated that STAT3 promoted 5-Fu resistance in CRC. Mechanistically, STAT3 triggered autophagy via Mcl-1 to induce cancer chemoresistance. Our results show that STAT3 regulates 5-Fu resistance in CRC by promoting Mcl-1–dependent cytoprotective autophagy. Our results provide a novel role of STAT3 and may offer a new approach for managing CRC 5-Fu resistance.     

下调ERp57抑制食管癌细胞增殖、迁移和侵袭

目的:分析内质网驻留蛋白57(ERp57)在食管鳞癌组织中的表达情况以及下调ERp57对食管癌细胞TE-1生物学功能的影响。方法:GEPIA数据库分析食管癌中ERp57的表达;通过荧光定量PCR和Western blot检测临床食管癌标本及细胞株中ERp57的表达;利用shRNA沉默TE-1细胞内ERp57后,通过CCK8检测细胞增殖、TUNEL检测细胞凋亡、划痕检测细胞迁移、Transwell检测细胞侵袭。结果:食管癌组织中ERp57的mRNA和蛋白的表达水平均高于癌旁组织(P<0.05),食管癌细胞中ERp57的mRNA及蛋白的表达高于食管上皮细胞(P<0.05)。沉默ERp57使TE-1细胞的增殖能力减弱、凋亡比例增加,并减弱了TE-1细胞的迁移及侵袭能力。结论:沉默ERp57表达能够抑制食管癌细胞TE-1的增殖、迁移、侵袭,可为食管癌研究提供理论依据。     

Glucose-regulated protein 58 modulates cell invasiveness and serves as a prognostic marker for cervical cancer

Human papilloma virus infection is critical but not sufficient to cause cervical cancer. Molecular markers of cervical carcinogenesis are essential. The aim of this study was to identify aberrantly expressed proteins in cervical cancer and determine their clinical significance. A two-dimensional polyacrylamide gel electrophoresis (2-DE) proteomic strategy was used for screening candidate proteins. Immunoblotting and immunohistochemical (IHC) analyses were performed to confirm the results of 2-DE, and the clinical significance was estimated. Glucose-regulated protein 58 (Grp58) was overexpressed in 73% of cancers. The IHC staining showed that the Grp58 histoscore was significantly higher in patients with adenocarcinoma (AD) compared with squamous cell carcinoma (P < 0.05). Grp58 staining was intense in AD with a penetration depth greater than half of the cervical stroma (P = 0.033). High Grp58 expression was associated with low overall survival and recurrence-free survival (RFS) rates (P = 0.007 and P = 0.013, respectively). In multivariate analysis, high Grp58 expression (P = 0.042) and lymph node metastasis (P = 0.026) were determined as independent prognostic factors for RFS. Patients exhibiting both high Grp58 expression and lymph node metastasis displayed poorer outcomes than the other patient groups. In functional studies, knockdown of Grp58 in HeLa cells led to decreased cell invasiveness and inhibition of lung metastasis in a xenograft mouse model. In conclusion, Grp58 serves as a potent prognostic factor of cervical AD. Estimation of the Grp58 index in conjunction with the lymph node metastasis status might aid in predicting the prognosis of cervical AD.     

Minecoside promotes apoptotic progression through STAT3 inactivation in breast cancer cells

Breast cancer is one of the most common malignant tumors in women worldwide, and is a major cause of mortality and morbidity in cancer patients. Constitutive activation of STAT3 has been found in a variety of malignant tumors, including breast cancer. Since STAT3 activation is capable of regulating various important features of tumor cells, identification of a novel STAT3 inhibitor is considered a potential strategy for treating breast cancer. The aim of the present study was to examine whether minecoside (MIN), an active compound extracted from Veronica peregrina L., exerts an antitumor effect by inhibiting STAT3 signaling pathway in MDA-MB-231 cells. The results revealed that MIN inhibited the constitutive STAT3 activation in a dose- and time-dependent manner. MIN also blocked the nuclear translocation of STAT3 and suppressed STAT3-DNA binding. In addition, MIN downregulated the STAT3-mediated expression of proteins such as Bcl-xL, Bcl-2, CXCR4, VEGF, and cyclin D1. Subsequently, MIN promoted the caspase-dependent apoptosis in MDA-MB-231 cells. Overall, results of the present study provide evidence that MIN exerted anticancer activity via inhibition of the STAT3 signaling pathway. Further studies using animal models are required to determine the potential of this molecule as an anticancer drug.     

Morusin induces cell death through inactivating STAT3 signaling in prostate cancer cells

STAT3 has been recognized as an efficacious drug target for prostate cancer because of its constitutive activation in this fatal disease. We recently identified the root bark of Morus alba Linn. as a potential STAT3 inhibitor among 33 phytomedicines traditionally used in Korea. Morusin, an active compound isolated from the root bark of Morus alba, has shown anti-oxidant and anti-inflammatory effects. In the present study, we examined whether morusin has a potential as an anti-cancer agent in prostate cancer. We found that morusin suppressed viability of prostate cancer cells, but little effect in normal human prostate epithelial cells. Morusin also reduced STAT3 activity by inhibiting its phosphorylation, nuclear accumulation, and DNA binding activity. In addition, morusin down-regulated expression of STAT3 target genes encoding Bcl-xL, Bcl-2, Survivin, c-Myc and Cyclin D1, which are involved in regulation of apoptosis and cell cycle. Furthermore, morusin induced apoptosis in human prostate cancer cells by reducing STAT3 activity. Taken together, these results suggest that morusin could be a potentially therapeutic agent for prostate cancer by reducing STAT3 activity and inducing apoptosis.     

STAT3作为一种新的肺肿瘤标志物的实验研究

目的探讨STAT3对肺腺癌早期诊断的价值及能否成为一种新的肺肿瘤标志物。方法采用荧光定量PCR、免疫组织化学PV法分别检测人肺腺癌细胞A549和正常人胚肺细胞MRC-5中STAT3、CEA、CA125 mRNA和蛋白表达情况,分析在人肺腺癌细胞A549中STAT3 mRNA分别与CEA、CA125 mRNA表达的相关性。结果(1)STAT3、CEA、CA125 mRNA在人肺腺癌细胞A549中的表达均明显高于它们各自在正常人胚肺细胞MRC-5中的表达,且STAT3 mRNA的表达与临床上常用的肺肿瘤标志物CEA、CA125 mRNA的表达均呈正相关。(2)STAT3在人肺腺癌细胞A549诊断中的敏感性(92.2%)与准确性(91.3%)均高于CEA、CA125。结论 STAT3有望成为一种新的肺肿瘤标志物用于临床。     

乙醛脱氢酶1作为喉癌Hep-2细胞系肿瘤干细胞标志物的实验研究

目的 探讨乙醛脱氢酶1(ALDH1)在人喉癌Hep-2细胞系中的表达,观察ALDH1高表达细胞的体外生长特性,确定喉癌Hep-2细胞系肿瘤干细胞标志物.方法 采用荧光细胞化学染色和流式细胞术观察和检测喉癌Hep-2细胞系中的ALDH1的表达.采用流式分选术分离ALDH1高表达细胞,以四甲基偶氮唑蓝(MTT)法观察ALDH1不同亚群细胞的体外增殖能力,以流式细胞术检测ALDH1高表达细胞的体外分化能力.采用裸鼠成瘤实验比较不同亚群细胞的成瘤能力.结果 喉癌Hep-2细胞系中ALDH1呈不同程度的表达,其中ALDH1高表达细胞占2.9％±0.6％.ALDH1高表达细胞的体外增殖能力高于ALDH1低表达和未分选细胞.在含血清的培养液中,经过6d培养,ALDH1高表达细胞由最初分选后的94.2％±3.8％下降至分选前水平.ALDH1高表达细胞的成瘤能力显著高于其他亚群.结论 喉癌Hep-2细胞系中,ALDH1高表达细胞具有很强的体外分化能力、增殖能力和成瘤能力,可以作为Hep-2细胞系肿瘤干细胞的标志物之一.     

Selection of radioresistant tumor cells and presence of ALDH1 activity in vitro

Background

Tumor resistance to radiotherapy has been hypothesized to be mediated by a tumor subpopulation, called cancer stem cells (CSCs). Based on the proposed function of CSCs in radioresistance, we explored the cancer stem cell properties of cells selected for radioresistance phenotype.

Materials and methods

A549 and SK-BR-3 cells were radioselected with four single doses of 4 or 3 Gy in intervals of 10-12 days and used for colony formation assay and γ-H2AX foci formation assay. Expression of putative stem cell markers, i.e. Sox2, Oct4, ALDH1, and CD133 were analyzed using Western blotting. A549 and SK-BR-3 cells sorted based on their ALDH1 activity were analyzed in clonogenic survival assays.

Results

Radioselected A549 and SK-BR-3 cells (A549-R, SK-BR-3-R) showed increased radioresistance and A549-R cells presented enhanced repair of DNA-double strand breaks. PI3K inhibition significantly reduced radioresistance of A549-R cells. Cell line specific differences in the expression of the putative CSC markers Sox2 and Oct4 were observed when parental and radioselected cells were compared but could not be directly correlated to the radioresistant phenotype. However, enzyme activity of the putative stem cell marker ALDH1 showed a correlation to radioresistance.

Conclusions

Subpopulations of pooled radioresistant colonies, selected by various radiation exposures were analyzed for the presence of putative stem cell markers. Although the pattern of Sox2, Oct4, and CD133 expression was not generally associated with radioresistance, presence of ALDH1 seems to be indicative for subpopulations with increased radioresistance.     

KLF3 is a crucial regulator of metastasis by controlling STAT3 expression in lung cancer

Lung cancer is one of the most common causes of cancer‐related mortality worldwide, which is partially due to its metastasis. However, the mechanism underlying its metastasis remains elusive. In this study, we showed that a low Krüppel‐like factor 3 (KLF3) expression level is correlated with a poor prognosis and TNM stages in clinical patients with lung cancer and further demonstrated that KLF3 expression is downregulated in lung cancer tissues compared with adjacent normal samples. In addition, bioinformatics analysis results showed that KLF3 expression is related to lung cancer epithelial‐mesenchymal transition (EMT). In vitro and in vivo experiments also showed that KLF3 silencing promotes lung cancer EMT and enhances lung cancer metastasis. More importantly, bioinformatics analysis and in vitro experiments indicated that the role of KLF3 in lung cancer metastasis is dependent on the STAT3 signaling pathway. Overall, our data indicated the crucial function of KLF3 in lung cancer metastasis and suggested opportunities to improve the therapy of patients with lung cancer.     

MicroRNA let-7 downregulates STAT3 phosphorylation in pancreatic cancer cells by increasing SOCS3 expression

Although dispensable for normal pancreatic function, STAT3 signaling is frequently activated in pancreatic cancers. Consistent downregulation of expression of microRNA let-7 is also characteristic of pancreatic ductal adenocarcinoma (PDAC) biopsy specimens. We demonstrate in this study that re-expression of let-7 in poorly-differentiated PDAC cell lines reduced phosphorylation/activation of STAT3 and its downstream signaling events and reduced the growth and migration of PDAC cells. Let-7 re-expression did not repress expression of STAT3 protein or its activator cytokine interleukin 6 (IL-6). However, let-7 re-expression enhanced cytoplasmic expression of suppressor of cytokine signaling 3 (SOCS3), which blocks STAT3 activation by JAK2. Our study thus identified a mechanism by which STAT3 signaling can be inhibited in pancreatic cancer cells by modifying let-7 expression.     

STAT3磷酸化调控乳腺癌髓系来源抑制细胞介导T细胞免疫抑制的机制研究

  目的   检测STAT3在乳腺癌MDSCs中的磷酸化状态及其对MDSCs免疫抑制活性的影响。   方法  收集脐血单个核细胞,免疫磁珠的方法分选其中CD33+细胞,体外与乳腺癌细胞系MDA-MB-231共孵育诱导MDSC生成。Western blot方法分别检测IDO和STATs的表达与磷酸化情况。MDSCs与健康供者外周血T淋巴细胞共孵育,分别加入1-MT和JSI-124来抑制IDO功能和STAT3磷酸化,利用MTT实验和ELISA检测各组T细胞的增殖和细胞因子分泌。   结果  Western blot检测发现体外诱导的MDSCs中IDO表达明显增加,同时伴STAT3磷酸化水平升高。加入JSI-124后pSTAT3和IDO表达明显降低。MTT实验中MDSCs明显抑制T细胞增殖,加用IDO特异性抑制剂1-MT或STAT3抑制剂JSI-124后T细胞增殖抑制明显改善（P < 0.05）,且1-MT组和JSI-124组之间差异无统计学意义。ELISA结果显示MDSCs显著抑制T细胞分泌IFN-γ,促进TGF-β、IL-10释放（P < 0.05）。而加用1-MT或JSI-124后,IFN-γ分泌水平升高,而TGF-β、IL-10分泌水平降低（P < 0.05）,而1-MT组和JSI-124组之间差异无统计学意义。   结论   MDSCs中磷酸化STAT3水平升高导致IDO过表达;STAT3的特异性抑制剂JSI-124可以逆转MDSCs对T细胞增殖和Th1类因子分泌的抑制作用。