MAP2 Splicing is Altered in Huntington's Disease

Dendritic alteration of striatal medium spiny neurons is one of the earliest morphological abnormalities in Huntington's disease (HD). The main microtubule‐associated protein in dendrites is MAP2. The low‐molecular weight isoforms of MAP2 (LMW‐MAP2) are the juvenile forms resulting from exclusion of the sequence encoded by exons E7‐E9 and are downregulated after the early stages of neuronal development when E7‐E9 exon‐including high‐molecular weight isoforms (HMW‐MAP2) are favored. Splicing alteration has recently been proposed to contribute to HD in view of two pathogenic missplicing events resulting in a highly toxic N‐terminal version of mutant huntingtin and in a detrimental imbalance in MAP Tau isoforms with three or four tubulin‐binding repeats. Both splicing events are postulated targets of the SR splicing factor SRSF6 which has recently been reported to be dramatically altered in HD. SR proteins often regulate functionally related sets of genes and SRSF6 targets are enriched in genes involved in brain organogenesis including several actin‐and tubulin‐binding proteins. Here we hypothesized that MAP2 might be target of SRSF6 and altered in HD. By SRSF6 knockdown in neuroblastoma cells, we demonstrate that splicing of MAP2 E7‐E9 exons is affected by SRSF6. We then show a disbalance in LMW and HMW MAP2 mRNA isoforms in HD striatum in favor of the juvenile LMW forms together with a decrease in total MAP2 mRNA. This is accompanied by a global decrease in total MAP2 protein due to almost total disappearance of HMW‐MAP2 isoforms with preservation of LMW‐MAP2 isoforms. Accordingly, the predominant dendritic MAP2 staining in striatal neuropil of control subjects is absent in HD cases. In these, MAP2‐immunoreactivity is faint and restricted to neuronal cell bodies often showing a sharp boundary at the base of dendrites. Together, our results highlight the importance of splicing alteration in HD and suggest that MAP2 alteration contributes to dendritic atrophy.     

High nitric oxide production,secondary to inducible nitric oxide synthase expression,is essential for regulation of the tumour‐initiating properties of colon cancer stem cells

Chronic inflammation is a leading cause of neoplastic transformation in many human cancers and especially in colon cancer (CC), in part due to tumour promotion by nitric oxide (NO) generated at inflammatory sites. It has also been suggested that high NO synthesis, secondary to inducible NO synthase (iNOS) expression, is a distinctive feature of cancer stem cells (CSCs), a small subset of tumour cells with self‐renewal capacity. In this study we explored the contribution of NO to the development of colon CSC features and evaluated potential strategies to treat CC by modulating NO production. Our data show an integral role for endogenous NO and iNOS activity in the biology of colon CSCs. Indeed, colon CSCs with high endogenous NO production (NO^high) displayed higher tumourigenic abilities than NO^low fractions. The blockade of endogenous NO availability, using either a specific iNOS inhibitor or a genetic knock‐down of iNOS, resulted in a significant reduction of colon CSC tumourigenic capacities in vitro and in vivo. Interestingly, analysis of genes altered by iNOS‐directed shRNA showed that the knockdown of iNOS expression was associated with a significant down‐regulation of signalling pathways involved in stemness and tumour progression in colon CSCs. These findings confirm that endogenous NO plays an important role in defining the stemness properties of colon CSCs through cross‐regulation of several cellular signalling pathways. This discovery could shed light on the mechanisms by which NO induces the growth and invasiveness of CC, providing new insights into the link between inflammation and colon tumourigenesis. Copyright © 2015 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

The cancer stem cell marker CD133 has high prognostic impact but unknown functional relevance for the metastasis of human colon cancer

In colon cancer, CD133 has recently been used to enrich for a subset of tumour cells with tumour‐initiating capabilities and was therefore suggested to mark colon cancer stem cells. However, this molecule has surprisingly been shown to lack functional importance for tumour initiation itself. Herein, we investigated whether CD133 may be relevant for colon cancer metastasis in patients, and as metastasis requires several additional biological characteristics besides tumour initiation, we examined the effects of knocking down CD133 expression in colon cancer cell lines on proliferation, migration, invasion, and colony formation. We demonstrate that high CD133 expression correlates strongly with synchronous liver metastasis in a matched case–control collection, while siRNA‐mediated knock down of this factor has no significant effect on the mentioned biological characteristics. Thus, we conclude that CD133 expression is a marker with high prognostic impact for colon cancer, while it seems to have no obvious functional role as a driving force of this malignancy. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Sequential expression of miR‐182 and miR‐503 cooperatively targets FBXW7, contributing to the malignant transformation of colon adenoma to adenocarcinoma

Genetic changes in colon cancer are known to parallel the tissue abnormalities associated with the disease, namely adenoma and adenocarcinoma. The role of microRNA dysregulation in dysplastic progression, however, is not well understood. Here, we show that miR‐182 and miR‐503 undergo sequential up‐regulation and drive the progression of colon adenoma to adenocarcinoma by cooperatively down‐regulating the tumour suppressor FBXW7. We identified that increased expression of miR‐182 is a feature of adenomas. A subsequent increase in miR‐503 expression works cooperatively with miR‐182 to induce transformation of an adenoma to adenocarcinoma. We show that introducing miR‐503 into AAC1 cells, which are derived from a benign adenoma, confers tumourigenic potential. We also demonstrated that blocking both miR‐182 and miR‐503 in HCT116 colon cancer cells resulted in increased FBXW7 expression and significantly reduced tumour size in xenograft models. We confirmed relevance of these results in patients by examining the expression levels of miR‐182 and miR‐503 in over 200 colon cancer patients with 12 year survival outcome data. Decreased patient survival was correlated with elevated expression of both miRNAs, suggesting that elevated levels of both miR‐182 and miR‐503 define a novel prognostic biomarker for colon cancer patients. In conclusion, we show that a sequential expression of miR‐182 and miR‐503 in benign adenoma cooperatively regulates the tumour suppressor FBXW7, contributing to the malignant transformation of colon adenoma to adenocarcinoma and miR‐182 and miR‐503 may prove to be novel therapeutic targets. Array data are available at: http://www.oncomir.umn.edu/ Copyright © 2014 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd     

Tumour stroma‐derived lipocalin‐2 promotes breast cancer metastasis

Tumour cell‐secreted factors skew infiltrating immune cells towards a tumour‐supporting phenotype, expressing pro‐tumourigenic mediators. However, the influence of lipocalin‐2 (Lcn2) on the metastatic cascade in the tumour micro‐environment is still not clearly defined. Here, we explored the role of stroma‐derived, especially macrophage‐released, Lcn2 in breast cancer progression. Knockdown studies and neutralizing antibody approaches showed that Lcn2 contributes to the early events of metastasis in vitro. The release of Lcn2 from macrophages induced an epithelial–mesenchymal transition programme in MCF‐7 breast cancer cells and enhanced local migration as well as invasion into the extracellular matrix, using a three‐dimensioanl (3D) spheroid model. Moreover, a global Lcn2 deficiency attenuated breast cancer metastasis in both the MMTV–PyMT breast cancer model and a xenograft model inoculating MCF‐7 cells pretreated with supernatants from wild‐type and Lcn2‐knockdown macrophages. To dissect the role of stroma‐derived Lcn2, we employed an orthotopic mammary tumour mouse model. Implantation of wild‐type PyMT tumour cells into Lcn2‐deficient mice left primary mammary tumour formation unaltered, but specifically reduced tumour cell dissemination into the lung. We conclude that stroma‐secreted Lcn2 promotes metastasis in vitro and in vivo, thereby contributing to tumour progression. Our study highlights the tumourigenic potential of stroma‐released Lcn2 and suggests Lcn2 as a putative therapeutic target. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

SRSF9/SRp30c通过调控GRβ对胶质瘤细胞增殖和迁移的影响

目的:探讨富含丝氨酸-精氨酸剪切因子9/富含丝氨酸-精氨酸蛋白30c(SRSF9/SRp30c)和糖皮质激素受体β(GRβ)在胶质瘤细胞中的表达及两者之间的关系。方法:用小干扰RNA(siRNA)靶向干扰胶质瘤U87细胞中SRSF9的表达,同时用慢病毒将短发卡RNA(shRNA)转染细胞,构建SRSF9敲减的U87稳转细胞株,通过荧光显微镜观察并检测转染情况。通过RT-q PCR和Western blot法检测SRSF9/SRp30c和GRβ的表达水平,CCK-8和细胞集落形成实验检测细胞的增殖能力,划痕实验检测细胞的迁移能力。结果:用2种方法敲减SRSF9后,SRSF9/SRp30c表达均降低,GRβ的表达水平也随之下降,差异有统计学意义(P0.05)。荧光显微镜观察结果表明,成功构建了稳转细胞株,转染效率超过80%。CCK-8实验和细胞集落形成实验的结果表明U87细胞在敲减SRSF9后,细胞活力和集落形成能力降低,差异有统计学意义(P0.05);划痕实验结果表明U87细胞在敲减SRSF9后,迁移能力明显减弱,差异有统计学意义(P0.05)。结论:SRSF9/SRp30c可通过调控GRβ促进胶质瘤细胞的增殖和迁移。     

Coordinated expression of REG4 and aldehyde dehydrogenase 1 regulating tumourigenic capacity of diffuse‐type gastric carcinoma‐initiating cells is inhibited by TGF‐β

Aldehyde dehydrogenase 1 (ALDH1) has been shown to serve as a marker for cancer‐initiating cells (CICs), but little is known about the regulation of the CIC functions of ALDH1+ cancer cells. We isolated ALDH1+ cells from human diffuse‐type gastric carcinoma cells and characterized these cells using an Aldefluor assay. ALDH1+ cells constituted 5–8% of the human diffuse‐type gastric carcinoma cells, OCUM‐2MLN and HSC‐39; were more tumourigenic than ALDH1? cells; and were able to self‐renew and generate heterogeneous cell populations. Using gene expression microarray analyses, we identified REG4 (regenerating islet‐derived family, member 4) as one of the genes up‐regulated in ALDH1+ cells, and thus as a novel marker for ALDH1+ tumour cells. Induced expression of REG4 enhanced the colony‐forming ability of OCUM‐2MLN cells, while knockdown of REG4 inhibited the tumourigenic potential of ALDH1+ cells. We further found that TGF‐β signalling reduces the expression of ALDH1 and REG4, and the size of the ALDH1+ cell population. In human diffuse‐type gastric carcinoma tissues, the expression of ALDH1 and REG4 correlated with each other, as assessed by immunohistochemistry, and ALDH1 expression correlated inversely with Smad3 phosphorylation as a measure of TGF‐β signalling. These findings illustrate that, in diffuse‐type gastric carcinoma, REG4 is up‐regulated in ALDH1+ CICs, and that the increased tumourigenic ability of ALDH1+ cells depends on REG4. Moreover, TGF‐β down‐regulates ALDH1 and REG4 expression, which correlates with a reduction in CIC population size and tumourigenicity. Targeting REG4 in ALDH1+ CICs may provide a novel strategy in the treatment of diffuse‐type gastric carcinoma. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

SRSF2基因突变与髓系肿瘤

 剪接因子在真核生物前体mRNA的成熟过程中发挥重要作用,SR蛋白家族是常见的剪接因子之一。 SRSF2属于SR蛋白家族,对mRNA剪接、转录、维持DNA的稳定性及细胞增殖过程中发挥重要作用,SRSF2基因突变在髓系肿瘤（如：骨髓增生异常综合征,慢性粒单核细胞白血病等）检出率较高,并且可能与疾病的表型及预后相关。本文就SRSF基因及其突变的最新研究进展,及其与髓系肿瘤的关系做一综述。     

The haematopoietic specific signal transducer Vav1 is aberrantly expressed in lung cancer and plays a role in tumourigenesis

Lung cancer is the leading cause of cancer death worldwide. The spectrum of aberrations affecting signalling pathways in lung cancer pathogenesis has not been fully elucidated. Physiological expression of Vav1 is restricted to the haematopoietic system, where its best‐known function is as a GDP/GTP nucleotide exchange factor for Rho/RacGTPases, an activity strictly controlled by tyrosine phosphorylation downstream of cell surface receptors. Here we find Vav1 expression in 42% of 78 lung cancer cell lines analysed. Moreover, immunohistochemical analysis of primary human lung cancer tissue samples revealed Vav1 expression in 26/59 malignant samples, including adenocarcinoma, squamous cell carcinoma and bronchioloalveolar carcinoma. Stronger Vav1 staining was associated with larger tumour size. siRNA‐mediated knockdown of Vav1 in lung cancer cells reduced proliferation in agar and tumour growth in nude mice, while control siRNA had no effect, suggesting that Vav1 plays a critical role in the tumorigenicity of lung cancer cells. Vav1 is tyrosine‐phosphorylated in lung cancer cells following activation by the growth factors EGF and TGFα, suggesting its participation in signalling events in these cells. Depletion of Vav1 reduced Rac‐GTP activation and decreased expression of TGFα, an autocrine growth factor. These data suggest that Vav1 plays a role in the neoplastic process in lung cancer, identifying it as a potential therapeutic target for lung cancer therapy. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

SKA1 over‐expression promotes centriole over‐duplication,centrosome amplification and prostate tumourigenesis

Although spindle‐ and kinetochore‐associated protein 1 (Ska1) has previously been identified as essential for proper chromosome segregation, it is unknown whether it plays a role in tumour development. Here, we report that Ska1 over‐expression promotes prostate tumourigenesis. Immunohistochemistry and quantitative RT–PCR analysis revealed that Ska1 was over‐expressed in human prostatic intra‐epithelial neoplasia (PIN), the most likely prostate cancer precursor, and adenocarcinomas. Up‐regulation of Ska1 protein was also found to be tumour‐specific in breast, lung and other common human cancers. Importantly, prostate‐specific up‐regulation of Ska1 in a transgenic mouse model resulted in spontaneous tumourigenesis. Furthermore, in addition to its abundance in spindle microtubules and the outer kinetochore interface during mitosis, Ska1 was enriched at centrosomes in cultured cells. Depletion of Ska1 caused a failure of centrosome duplication, whilst Ska1 over‐expression led to centrosome amplification in human prostate epithelial cells via the induction of centriole over‐duplication. These epithelial cells harbouring extra centrosomes switched from a non‐tumourigenic to a tumourigenic state in nude mice. Taken together, these data indicate that Ska1 over‐expression promotes tumourigenesis. Copyright © 2014 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd     

HOPX is methylated and exerts tumour‐suppressive function through Ras‐induced senescence in human lung cancer

HOPX acts as a tumour suppressor in various cancers. However, the regulation of HOPX in human lung cancer as well as the mechanism underlying its tumour‐suppressive function has not yet been well elucidated. Here we investigated the epigenetic regulation and molecular mechanism by which HOPX exerts growth inhibitory effects. We found that HOPX was down‐regulated in 12 out of 13 lung cancer cell lines and in 69 out of 120 primary lung tumours at mRNA and protein levels. Patients with lung adenocarcinoma (ADC) exhibited significantly more positive staining of HOPX protein compared with lung squamous cell carcinoma (SCC) (p =0.036). Again in ADC, patients with higher HOPX expression had a significantly longer disease‐free survival (p =0.001). Methylation analysis showed that down‐regulation of HOPX was associated with DNA methylation (p =0.011). To analyse the function of HOPX in lung cancer cells, stable transfection with an expression vector of HOPX was performed. It turned out that HOPX inhibited tumour cell proliferation rate, migration, and invasion, and, more interestingly, forced expression of HOPX enhanced cellular senescence via activation of oncogenic Ras and the downstream MAPK pathway, which in turn led to decreased MDM2 and increased p21. On the contrary, knockdown of HOPX by siRNA resulted in reduced Ras activity, inactivation of the MAPK pathway, and decreased p21 levels, accompanied by reduced cellular senescence. Additionally, the HOPX‐induced senescence pathway was also active in human bronchial epithelial cells. Taken together, our data suggest that down‐regulation of HOPX was related to DNA methylation and that HOPX exerts tumour‐suppressive activity by oncogenic Ras‐induced cellular senescence in lung cancer cells. Copyright © 2014 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

CD49f剪接异构体在不同细胞系中的表达

目的比较CD49f选择性剪接异构体在人不同来源干细胞以及结肠癌细胞系中的表达,并构建特定异构体过表达载体用于功能研究。方法 RT-PCR及real-time PCR检测CD49f选择性剪接异构体在不同细胞中的表达;分子克隆方法构建各异构体的慢病毒过表达载体;流式细胞计量术、Western blot及real-time PCR检测CD49f各异构体的过表达;Transwell方法检测细胞侵袭能力的改变。结果人胚胎干细胞系H9中表达CD49f异构体B,而上皮类细胞仅表达异构体A;间质细胞中二者均有表达,但异构体A表达多于异构体B;检测的4个结肠癌细胞系中CD49f异构体A和B均有表达,其中HT29和HCT116中以异构体A为主,而HCT8和LoVo中异构体B的表达更为明显。构建的慢病毒表达载体可使HT29中CD49f异构体A和B获得特异性过表达,其中异构体B的过表达使HT29的侵袭能力增加。结论不同类型细胞中CD49f选择性剪接异构体A和B的表达存在显著差异,二者的生物学功能具有差别。     

Non-fitness status of peripheral NK cells defined by decreased NKp30 and perforin,and increased soluble B7H6, in cervical cancer patients

The NKp30 receptor is one of the three natural cytotoxic receptors reported in NK cells. This receptor is codified by the NCR3 gene, which encodes three isoforms, a consequence of the alternative splicing of exon 4. A greater expression of the three isoforms (A, B, and C), along with low levels of the NKp30 ligand B7H6, has been reported as a positive prognostic factor in different cancer types. Here, in patients with cervical cancer and precursor lesions, we report an altered immune-phenotype, characterized by non-fitness markers, that correlated with increased disease stage, from CIN 1 to FIGO IV. While overall NK cell numbers increased, loss of NKp30⁺ NK cells, especially in the CD56^dim subpopulation, was found. Perforin levels were decreased in these cells. Decreased expression of the NKp30 C isoform and overexpression of soluble B7H6 was found in cervical cancer patients when compared against healthy subjects. PBMCs from healthy subjects downregulated NKp30 isoforms after co-culture with B7H6-expressing tumour cells. Taken together, these findings describe a unique down-modulation or non-fitness status of the immune response in cervical cancer, the understanding of which will be important for the design of novel immunotherapies against this disease.     

Targeting FLIP and Mcl‐1 using a combination of aspirin and sorafenib sensitizes colon cancer cells to TRAIL

The multikinase inhibitor sorafenib is highly effective against certain types of cancer in the clinic and prevents colon cancer cell proliferation in vitro. Non‐steroidal anti‐inflammatory drugs, such as acetylsalicylic acid (aspirin), have shown activity against colon cancer cells. The aims of this study were to determine whether the combination of aspirin with sorafenib has enhanced anti‐proliferative effects and increases recombinant human tumour necrosis factor‐related apoptosis‐inducing ligand (rhTRAIL)‐induced apoptosis in the human SW948, Lovo, Colo205, Colo320, Caco‐2 and HCT116 colon cancer cell lines. In four cell lines, aspirin strongly stimulated the anti‐proliferative effects of sorafenib (～four‐fold enhancement) by inducing cell cycle arrest. Furthermore, combining low doses of aspirin (≤ 5 mm ) and sorafenib (≤ 2.5 µm ) greatly sensitized TRAIL‐sensitive and TRAIL‐resistant colon cancer cells to rhTRAIL, much more potently than either drug combined with rhTRAIL. The increase in rhTRAIL sensitivity was due to inhibition of FLIP and Mcl‐1 protein expression following aspirin and sorafenib co‐treatment, as confirmed by knock‐down studies. Next, the clinical relevance of targeting FLIP and Mcl‐1 in colon cancer was examined. Using immunohistochemistry, we found that Mcl‐1 expression was significantly increased in colon adenoma and carcinoma patient material compared to healthy colonic epithelium, similar to the enhanced FLIP expression we recently observed in colon cancer. These results underscore the potential of combining low doses of aspirin with sorafenib to inhibit proliferation and target the anti‐apoptotic proteins FLIP and Mcl‐1 in colon cancer cells. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Control of the heat stress‐induced alternative splicing of a subset of genes by hnRNP K

Pre‐mRNA splicing is widely repressed upon heat shock in eukaryotic cells. However, it has been shown that HSP105 pre‐mRNA is alternatively spliced in response to heat stress. Using RNAi screening in HeLa cells, we found that RNA‐binding proteins hnRNP K and PSF/SFPQ are necessary for the exon 12 exclusion of HSP105 during heat stress. Moreover, exon array analyses showed that a group of genes is alternatively spliced during heat stress in an hnRNP K‐dependent manner, whereas hnRNP K is not necessary for the stress‐induced alternative splicing of the remaining genes. Among the latter group, we found that SRp38/SRSF10 and SC35/SRSF2 are necessary for the inclusion of exon 13 of TNRC6A during heat stress. Thus, our study clearly showed that several RNA‐binding proteins are involved in the splicing regulation in response to heat stress in mammalian cells.     

EMILIN2 down‐modulates the Wnt signalling pathway and suppresses breast cancer cell growth and migration

EMILIN2 is an extracellular matrix (ECM) protein that exerts contradictory effects within the tumour microenvironment: it induces apoptosis in a number of tumour cells, but it also enhances tumour neo‐angiogenesis. In this study, we describe a new mechanism by which EMILIN2 attenuates tumour cell viability. Based on sequence homology with the cysteine‐rich domain (CRD) of the Frizzled receptors, we hypothesized that EMILIN2 could affect Wnt signalling activation and demonstrate direct interaction with the Wnt1 ligand. This physical binding leads to decreased LRP6 phosphorylation and to the down‐modulation of β‐catenin, TAZ and their target genes. As a consequence, EMILIN2 negatively affects the viability, migration and tumourigenic potential of MDA‐MB‐231 breast cancer cells in a number of two‐ and three‐dimensional in vitro assays. EMILIN2 does not modulate Wnt signalling downstream of the Wnt–Frizzled interaction, since it does not affect the activation of the pathway following treatment with the GSK3 inhibitors LiCl and CHIR99021. The interaction with Wnt1 and the subsequent biological effects require the presence of the EMI domain, as there is no effect with a deletion mutant lacking this domain. Moreover, in vivo experiments show that the ectopic expression of EMILIN2, as well as treatment with the recombinant protein, significantly reduce tumour growth and dissemination of cancer cells in nude mice. Accordingly, the tumour samples are characterized by a significant down‐regulation of the Wnt signalling pathway. Altogether, these findings provide further evidence of the complex regulations governed by EMILIN2 in the tumour microenvironment, and they identify a key extracellular regulator of the Wnt signalling pathway. Copyright © 2013 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.