Induction of autophagy contributes to crizotinib resistance in ALK-positive lung cancer

Use of the inhibitor of ALK fusion onco-protein, crizotinib (PF02341066), has achieved impressive clinical efficacy in patients with ALK-positive non-small cell lung cancer. Nevertheless, acquired resistance to this drug occurs inevitably in approximately a year, limiting the therapeutic benefits of this novel targeted therapy. In this study, we found that autophagy was induced in crizonitib-resistant lung cancer cells and contributed to drug resistance. We observed that ALK was downregulated in the crizotinib-resistant lung cancer cell line, H3122CR-1, and this was causally associated with autophagy induction. The degree of crizotinib resistance correlated with autophagic activity. Activation of autophagy in crizotinib-resistant H3122CR-1 cells involved alteration of the Akt/mTOR signaling pathway. Furthermore, we demonstrated that chloroquine, an inhibitor of autophagy, could restore sensitivity of H3122CR-1 to crizotinib and enhance its efficacy against drug-resistant lung cancer. Thus, modulating autophagy may be worth exploring as a new strategy to overcome acquired crizonitib resistance in ALK-positive lung cancer.     

OPB-31121, a novel small molecular inhibitor,disrupts the JAK2/STAT3 pathway and exhibits an antitumor activity in gastric cancer cells

We investigated the mechanisms of action and antitumor effects of OPB-31121, a novel STAT3 inhibitor, in gastric cancer cells. OPB-31121 downregulated JAK2 and gp130 expression and inhibited JAK2 phosphorylation which leads to inhibition of STAT3 phosphorylation. OPB-31121 inhibited constitutively activated and IL-6-induced JAK/STAT signaling pathway. OPB-31121 decreased cell proliferation in both gastric cancer cells and in a xenograft model, induced the apoptosis of gastric cancer cells, inhibited the expression of antiapoptotic proteins, and showed synergism with 5-fluorouracil and cisplatin. Taken together, our study suggests that STAT3 inhibition with OPB-31121 can be tested in patients with gastric cancer.     

DNMT3a通过STAT3及RAD51影响胰腺癌细胞对奥沙利铂敏感性的研究

目的:检测DNMT3a在胰腺癌细胞中的表达及对奥沙利铂（oxaliplatin，OXA）敏感性的影响，探讨DNMT3a对胰腺癌细胞奥沙利铂敏感性影响的机制。方法:MTT法检测奥沙利铂对人胰腺癌Panc-1细胞的增殖影响，及下调DNMT3a对Panc-1细胞奥沙利铂敏感性的影响。Western blot检测siDNMT3a对DNMT3a蛋白表达的影响，检测奥沙利铂及下调DNMT3a对γ-H2AX、RAD51、p-STAT3和STAT3蛋白表达的影响。流式细胞仪检测奥沙利铂及联合下调DNMT3a对Panc-1细胞凋亡的影响。结果:奥沙利铂能够以浓度依赖方式抑制胰腺癌Panc-1细胞的增殖。奥沙利铂能够引起DNA损伤、γ-H2AX上调及RAD51增高，同时引起STAT3通路的一过性活化。下调DNMT3a表达能够明显增加Panc-1细胞对奥沙利铂的敏感性，抑制STAT3一过性活化，并抑制RAD51表达，促进DNA损伤，进而增加奥沙利铂诱导Panc-1细胞的凋亡。结论:下调DNMT3a表达能够通过抑制STAT3活化及增加DNA损伤增加胰腺癌细胞对奥沙利铂的敏感性，DNMT3a有望成为胰腺癌新的治疗靶点。     

Inhibiting autophagy increases epirubicin's cytotoxicity in breast cancer cells

Chemotherapy, radiotherapy, and endocrinotherapy are documented to induce autophagy among breast cancer cells, but the role of autophagy in this disease has been attributed as cytoprotective as well as tumor‐suppressing. Thus we studied MDA‐MB‐231 and SK‐BR‐3 breast cancer cell lines treated with epirubicin (EPI) to assess autophagy and apoptosis. We found out that EPI induced apoptosis and autophagy in both cell lines. The lysosomal inhibitor bafilomycin A1 inhibited cellular autophagy and enhanced EPI‐triggered apoptosis, perhaps due to inhibition of autolysosome formation, which then inhibited autophagic effects of engulfing and clearing damaged mitochondria. This inhibition increased mitochondrial cytochrome C release which augmented epirubicin‐induced caspase‐dependent apoptosis and cytotoxicity. In addition, the lysosomal neutralizing agent ammonia chloride (AC), and Atg7 knockdown by siRNA, could inhibit epirubicin‐triggered autophagy, enhance cytotoxicity, and increase caspase‐9‐ and caspase‐3‐dependent apoptosis. Thus, autophagy plays a prosurvival role in EPI‐treated MDA‐MB‐231 and SK‐BR‐3 cells, and autophagy inhibition can potentially reverse this effect and increase the cytotoxicity of EPI.     

Anti-cancer effect of tectochrysin in NSCLC cells through overexpression of death receptor and inactivation of STAT3

Phenolic compounds (flavonoids and phenolic acid derivatives) are the most important pharmacologically active ingredients, and these compounds could inhibit proliferation of human cancer cells by inducing of apoptotic cell death. Here we focused on the anticancer effects of tectochrysin on human non-small-cell lung cancer (NSCLC) cells and its mechanism of action. We analysed the activity of tectochrysin on NSCLC cells (A549 and NCI-H460) by use of Western blot analysis for major apoptotic proteins and death receptor expression. We also used EMSA for effects on STAT3 DNA binding activity. Tectochrysin (0–80 μM) suppressed the growth of A549 and NCI-H460 lung cancer cells by inducing of apoptotic cell death in a concentration dependent manner. Expression of DR3 and Fas as well as DR downstream pro-apoptotic proteins including cleaved caspase-3, cleaved caspase-8, cleaved caspase-9 and Bax were concomitantly increased, but the expression of anti-apoptotic proteins; Bcl-2 was decreased in both cancer cells. In addition, tectochrysin treatment also inhibited phosphorylation of STAT3 in A549 and NCI-H460 cells. However, deletion of DR3 and Fas by small interfering RNA significantly reversed tectochrysin-induced cell growth inhibitory effect as well as down regulation of STAT3 in A549 and NCI-H460 lung cancer cells. Pull down assay and docking model showed interaction of tectochrysin with STAT3. We propose that tectochrysin leads to apoptotic cell death in NSCLC cells through activation of DR3 and Fas expression via inhibition of STAT3 phosphorylation.     

RNA干扰技术沉默STAT3 对人肺癌细胞生长抑制的作用

 目的 探讨RNA干扰技术沉默STAT3基因表达对肺腺癌A549细胞的生长抑制作用。方法针对STAT3mRNA序列设计合成2对编码si RNA的DNA模板,构建pSUPER-si RNA-STAT3重组质粒,转染A549细胞;采用RT-PCR法检测重组质粒对STAT3基因表达的影响;在荧光显微镜下观察细胞的凋亡情况。结果 成功构建pSUPER-si RNA-STAT3重组质粒,并成功转染A549细胞。特异性si RNA片段能有效降低STAT3mRNA水平,最大干扰效率达85.32%,明显高于空质粒对照组;干扰作用于转染后24h即可出现,48h达高峰,72h降低。对应不同位点的两个si RNA片段对STAT3均可产生干扰作用,彼此间差别不大。在荧光显微镜下,与未转染细胞相比,转染si RNA的A549细胞中凋亡细胞所占比例明显增加。结论 pSUPER-si RNA-STAT3可抑制STAT3在人肺腺癌A549细胞中的表达,并抑制肿瘤细胞的生长,促进其凋亡。以STAT3为靶点的RNA干扰技术可望成为肺癌基因治疗的新方法。     

碳离子(^(12)C^(6+))抑制JAK2/STAT3通路促进肺癌中CD8^(+)T细胞浸润的研究北大核心CSCD

目的探索碳离子(^(12)C^(6+))照射后JAK2/STAT3通路的改变及下游蛋白FOXP3调控的肺癌中CD8+T细胞的浸润差异。方法基于C57BL/6小鼠Lewis荷瘤模型的RNA测序分析,筛选出碳离子照射后肺癌中显著改变的JAK2/STAT3通路及相关的差异表达基因及蛋白如FOXP3。利用R软件“GSVA”中ssGSEA免疫浸润算法,探索FOXP3与肺癌免疫微环境中主要免疫细胞浸润的相关性并基于碳离子联合STAT3抑制途径(氯硝柳胺)对肺癌中CD8+T细胞浸润进行分析。结果碳离子照射后,肺癌中JAK2/STAT3通路被抑制,相关基因和蛋白表达下调。基于ssGSEA算法的免疫评分显示,FOXP3表达与肺癌免疫微环境中CD8+T细胞浸润呈显著负相关。通过碳离子照射联合STAT3抑制剂氯硝柳胺,进一步明确了靶向JAK2/STAT3通路对于增加肺癌中CD8^(+)T细胞浸润的协同作用。结论碳离子(^(12)C^(6+))可以通过靶向JAK2/STAT3通路与免疫治疗发挥协同增效的作用。     

STAT3 mediates resistance to MEK inhibitor through microRNA miR-17

AZD6244 is a small molecule inhibitor of the MEK (MAP/ERK kinase) pathway currently in clinical trials. However, the mechanisms mediating intrinsic resistance to MEK inhibition are not fully characterized. To define molecular mechanisms of MEK inhibitor resistance, we analyzed responses of 38 lung cancer cell lines following AZD6244 treatment and their genome-wide gene expression profiles and identified a panel of genes correlated with sensitivity or resistance to AZD6244 treatment. In particular, ingenuity pathway analysis revealed that activation of the STAT3 pathway was associated with MEK inhibitor resistance. Inhibition of this pathway by JSI-124, a STAT3-specific small molecule inhibitor, or with STAT3-specific siRNA sensitized lung cancer cells to AZD6244 and induced apoptosis. Moreover, combining a STAT3 inhibitor with AZD6244 induced expression of BIM and PARP cleavage, whereas activation of the STAT3 pathway inhibited BIM expression and elicited resistance to MEK inhibitors. We found that the STAT3-regulated microRNA miR-17 played a critical role in MEK inhibitor resistance, such that miR-17 inhibition sensitized resistant cells to AZD6244 by inducing BIM and PARP cleavage. Together, these results indicated that STAT3-mediated overexpression of miR-17 blocked BIM expression and caused resistance to AZD6244. Our findings suggest novel approaches to overcome resistance to MEK inhibitors by combining AZD6244 with STAT3 or miR-17 inhibitors.     

Suppression of autophagy by CUB domain‐containing protein 1 signaling is essential for anchorage‐independent survival of lung cancer cells

CUB (C1r/C1s, urchin embryonic growth factor, BMP1) domain‐containing protein 1 (CDCP1) has been implicated in promoting metastasis of cancer cells through several mechanisms, including the inhibition of anoikis, which is cell death triggered by the loss of extracellular matrix interactions. However, the mechanism inhibiting cell death regulated by CDCP1 remains elusive. Inhibition of CDCP1 expression using small interfering RNA (siRNA) induced the cell death of suspended cancer cells without cleaving caspase‐3, a marker of apoptosis; cell death was not inhibited by a general caspase inhibitor, suggesting that the loss of CDCP1 induces caspase‐independent cell death. In contrast, knockdown of CDCP1 as well as protein kinase Cδ (PKCδ), a downstream effector of CDCP1, in a suspension culture of lung cancer cells resulted in marked induction of membranous microtubule‐associated protein 1 light chain 3 (LC3)‐II protein, a hallmark of autophagy, and caused the formation of an autophagosome structure visualized using green fluorescent protein‐tagged LC3‐II. Expression and phosphorylation of exogenous CDCP1 by Fyn kinase reduced the formation of autophagosomes and inhibited phosphorylation of CDCP1 by PP2, a Src kinase inhibitor or inhibited PKCδ by rottlerin, stimulating autophagosome formation. Moreover, death of suspended lung cancer cells induced by CDCP1 siRNA or by PKCδ siRNA was reduced by the autophagy inhibitor 3‐methyladenine. These results indicate that CDCP1‐PKCδ signaling plays a critical role in inhibiting autophagy, which is responsible for anoikis resistance of lung cancer cells.     

碳离子（12C6+）抑制JAK2/STAT3通路促进肺癌中CD8+ T细胞浸润的研究

目的 探索碳离子（¹²C⁶⁺）照射后JAK2/STAT3通路的改变及下游蛋白FOXP3调控的肺癌中CD8⁺T细胞的浸润差异。方法 基于C57BL/6小鼠Lewis荷瘤模型的RNA测序分析,筛选出碳离子照射后肺癌中显著改变的JAK2/STAT3通路及相关的差异表达基因及蛋白如FOXP3。利用R软件“GSVA”中ssGSEA免疫浸润算法,探索FOXP3与肺癌免疫微环境中主要免疫细胞浸润的相关性并基于碳离子联合STAT3抑制途径（氯硝柳胺）对肺癌中CD8⁺T细胞浸润进行分析。结果 碳离子照射后,肺癌中JAK2/STAT3通路被抑制,相关基因和蛋白表达下调。基于ssGSEA算法的免疫评分显示,FOXP3表达与肺癌免疫微环境中CD8⁺T细胞浸润呈显著负相关。通过碳离子照射联合STAT3抑制剂氯硝柳胺,进一步明确了靶向JAK2/STAT3通路对于增加肺癌中CD8⁺T细胞浸润的协同作用。结论 碳离子（¹²C⁶⁺）可以通过靶向JAK2/STAT3通路与免疫治疗发挥协同增效的作用。     

Suppression of SOCS3 in macrophages prevents cancer metastasis by modifying macrophage phase and MCP2/CCL8 induction

Inflammation has been demonstrated to play important roles in tumorigenesis, tumor progression, and metastasis. STAT3 has been shown to be frequently activated in a variety of human cancer cells and STAT3 signaling promotes the growth and survival of tumor cells. However, the role of STAT3 of myeloid cells associated with tumors is currently unknown. Suppressor of cytokine signaling-3 (SOCS3) has been shown to be a negative regulator of STAT3. In this study, we used macrophage specific SOCS3 conditional knockout (cKO) mice to investigate the effect of the hyperactivation of STAT3 in macrophages on tumor development and metastasis. In a subcutaneous transplantation model of B16F10 melanoma cells, although tumor sizes were not significantly different, SOCS3-cKO mice survived longer than wild-type (WT) mice did. SOCS3-cKO mice exhibited fewer lung and liver metastatic tumor nodules than WT mice when B16F10 was challenged intravenously. SOCS3(-/-) macrophages stimulated with tumor lysates in vitro exhibited prolonged STAT3 phosphorylation and produced less amount of TNFα and IL-6, and higher amount of MCP2/CCL8 than WT macrophages. MCP/CCL8 was induced via STAT3 and exhibited anti-tumor metastatic effect in WT mice. These data suggest that hyperactivation of STAT3 in myeloid cells simultaneously exerted an anti-inflammatory as well as anti-tumor effects. Thus, the targeted inhibition of SOCS3 activity in macrophages may be therapeutic for the suppression of tumor metastasis.     

Stathmin 1 inhibition amplifies ruxolitinib-induced apoptosis in JAK2V617F cells

The JAK/STAT pathway is constitutively activated in myeloproliferative neoplasms and can be inhibited by ruxolitinib, a selective JAK1/2 inhibitor. The JAK2^V617F mutation leads to constitutive STAT3 phosphorylation and potentially leads to inhibition of Stathmin 1 activity via STAT3. In support of this hypothesis, we found that, in HEL JAK2^V617F cells, ruxolitinib treatment decreased STAT3 and Stathmin 1 association, induced Stathmin 1 activation and microtubule instability. Silencing of Stathmin 1 significantly reduced cell proliferation and clonal growth, and increased apoptosis induced by ruxolitinib. Stathmin 1 silencing also prevented ruxolitinib-induced microtubule instability. To phenocopy the effect of Stathmin 1 inhibition, cells were treated with paclitaxel, a microtubule-stabilizing drug, in association or not with ruxolitinib; combined treatment significantly increased apoptosis, when compared to monotherapy. Notably, Stathmin 1 mRNA levels were highly expressed in CD34⁺ cells from primary myelofibrosis patients. We then proposed that an undesired effect of ruxolitinib treatment may constitute Stathmin 1 activation and microtubule instability in JAK2^V617F cells. Induction of microtubule stability, through Stathmin 1 silencing or paclitaxel treatment, combined with ruxolitinib could be an effective strategy for promoting apoptosis in JAK2^V617F cells.