Diet Induced Obesity Increases the Risk of Colonic Tumorigenesis in Mice

A large body of epidemiological data indicates that obesity increases the risk of colon cancer in humans. There are limited studies using rodent models where the relationship between obesity and colon cancer has been studied. In this study, wild-type diet-induced obese (DIO) mice and lean wild-type controls were used to investigate the influence of obesity on the risk of colon cancer. We hypothesized that the obese phenotype would exhibit increased colonic tumorigenesis. Colon cancer was chemically induced by injecting the mice with azoxymethane (AOM) at levels that we experimentally determined to result in equivalent AOM concentrations in circulating blood. Risk of colon cancer was assessed via microscopic examination of entire colons for aberrant crypts, aberrant crypt foci and proliferation levels. The DIO mice were found to have significantly more aberrant crypts and aberrant crypt foci as well as increased proliferation of colonocytes per mouse compared to wild-type control mice, supporting the epidemiological data that obesity increases the risk of colonic tumorigenesis.     

Prevention of Mammary Tumorigenesis in Acatalasemic Mice by Vitamin E Supplementation

Adult male and female acatalasemic (C3H/AnLCs^bCs^b), hypocatalasemic (C3H/AnLCs^cCs^c) and normal mice of C3H strain fed on regular laboratory chow for 15 months showed an increased incidence of spontaneous mammary tumor in the decreasing order of female acatalasemic, male acatalasemic, female hypocatalasemic and male hypocatalasemic mice. Normal mice did not develop mammary tumor. We conducted a prospective study with female acatalasemic mice, which showed the highest incidence of mammary tumor, to examine the preventive effect of vitamin E on mammary tumor. Female acatalasemic mice were fed on vitamin E-deficient (28 animals) and vitamin E-supplemented diet (25 animals) for 29 months. The incidence of mammary tumor in mice given the vitamin E-supplemented diet was 47%, while that in mice given vitamin E-deficient diet was 82% ( P <0.002). Mammary tumors were apparent after 9 months of vitamin E deprivation and after 14 months of vitamin E supplementation. Female normal mice did not develop mammary tumor during a comparable period of time. The mean catalase activity of mammary gland in acatalasemic mice was 18.8% of that in normal mice. The results indicate that vitamin E protects acatalasemic mice against the development of mammary tumor.     

Tumorigenesis facilitated by Pten deficiency in the skin: evidence of p53-Pten complex formation on the initiation phase

Pten, a tumor suppressor gene, is mutated in various human cancers and in hereditary cancer syndromes, such as Cowden disease. We have previously developed a knockout mouse in which Pten is specifically disrupted in the skin, resulting in hyperproliferation and spontaneous tumorigenesis of the skin keratinocytes. In this study, we further clarified the effects of Pten deficiency in tumorigenesis, by using a two-step model in intact skin of Pten knockout mouse. Although the conventional protocol requires serial exposures to DMBA and TPA, mice deficient for Pten developed skin papilloma within 6 weeks after a single exposure to DMBA, indicating that loss of Pten has a tumor-promoting effect. Serial exposure to DMBA-TPA ointments produced 10-fold more papillomas in the skin of knockout mice than in the wild-type counterpart, suggesting an increased rate of initiation. Therefore, we precisely examined the effect of DMBA. This treatment was highly apoptotic in wild-type mice, whereas the number of apoptotic cells was diminished in Pten-deficient skin. Moreover, primary keratinocytes isolated from Pten-deficient mice were also resistant to the apoptotic effect of DMBA. The status of p53, Pten proteins and downstream targets of p53, such as p21, 14-3-3, and Reprimo, were also examined, and we found that accumulation of p53 protein and up-regulation of p53 targets were delayed in Pten-knockout skin. These observations suggest that Pten is involved in rapid recruitment of p53 in the tumor initiation phase.     

Dietary Feeding of Grape Seed Extract Prevents Intestinal Tumorigenesis in APCmin/+ Mice

Chemopreventive effects and associated mechanisms of grape seed extract (GSE) against intestinal/colon cancer development are largely unknown. Herein, we investigated GSE efficacy against intestinal tumorigenesis in APC^min/+ mice. Female APC^min/+ mice were fed control or 0.5% GSE (wt/wt) mixed AIN-76A diet for 6 weeks. At the end of the experiment, GSE feeding decreased the total number of intestinal polyps by 40%. The decrease in polyp formation in the small intestine was 42%, which was mostly in its middle (51%) and distal (49%) portions compared with the proximal one. GSE also decreased polyp growth where the number of polyps of 1 to 2 mm in size decreased by 42% and greater than 2 mm in size by 71%, without any significant change in polyps less than 1 mm in size. Immunohistochemical analyses of small intestinal tissue samples revealed a decrease (80%–86%) in cell proliferation and an increase (four- to eight-fold) in apoptosis. GSE feeding also showed decreased protein levels of cyclooxygenase-2 (COX-2) (56%–64%), inducible nitric oxide synthase (iNOS) (58%–60%), and β-catenin (43%–59%) but an increased Cip1/p21-positive cells (1.9- to 2.6-fold). GSE also decreased cyclin D1 and c-Myc protein levels in small intestine. Together, these findings show the chemopreventive potential of GSE against intestinal polyp formation and growth in APC^min/+ mice, which was accompanied with reduced cell proliferation and increased apoptosis together with down-regulation in COX-2, iNOS, β-catenin, cyclin D1, and c-Myc expression, but increased Cip1/p21. In conclusion, the present study suggests potential usefulness of GSE for the chemoprevention of human intestinal/colorectal cancer.     

Pten signaling in gliomas

In 1997, the PTEN gene (phosphatase and tensin homolog deleted on chromosome 10) was identified as a tumor suppressor gene on the long arm of chromosome 10. Since then, important progress has been made with respect to the understanding of the role of the Pten protein in the normal development of the brain as well as in the molecular pathogenesis of human gliomas. This review summarizes the current state of the art concerning the involvement of aberrant Pten function in the development of different biologic features of malignant gliomas, such as loss of cell-cycle control and uncontrolled cell proliferation, escape from apoptosis, brain invasion, and aberrant neoangiogenesis. Most of the tumor-suppressive properties of Pten are dependent on its lipid phosphatase activity, which inhibits the phosphatidylinositol-3'-kinase (PI3K)/Akt signaling pathway through dephosphorylation of phosphatidylinositol-(3,4,5)-triphosphate. The additional function of Pten as a dual-specificity protein phosphatase may also play a role in glioma pathogenesis. Besides the wealth of data elucidating the functional roles of Pten, recent studies suggest a diagnostic significance of PTEN gene alterations as a molecular marker for poor prognosis in anaplastic astrocytomas and anaplastic oligodendrogliomas. Furthermore, the possibility of selective targeting of PTEN mutant tumor cells by specific pharmacologic inhibitors of members of the Pten/PI3K/Akt pathway opens up new perspectives for a targeted molecular therapy of malignant gliomas.     

mAFP基因转染树突状细胞免疫对小鼠诱发性肝癌发生的影响

目的:探讨用mAFP基因转染的树突状细胞(dendritic cells,DC)瘤苗免疫对小鼠诱发性肝癌发生的影响.方法:诱导、扩增C57BL/6J小鼠DC.将表达小鼠AFP基因(mAFP)的重组腺病毒转染DC.80只C57BL/6J雄性小鼠随机分为A、B、C、D组,每组20只.以单纯DC为A组;将表达mAFP基因的重组腺病毒转染DC(pAdBM5-mAFP-DCs)为B组;表达mAFP基因的质粒DNA(pAdBM5-mAFP)为C组;以单纯PBS(磷酸缓冲液)注射为对照组D组.免疫方法:实验组在每只小鼠的左胁部注射5×105个细胞(0.1ml/资),连续免疫3天,以后每7天接种疫苗1次,继续免疫4次.正常对照组,仅注射0.1ml PBS.在接种免疫的同时,给以二乙基亚硝胺(DEN)、四氯化碳(CCl4)和乙醇联合诱癌.诱癌20周后处死小鼠,检查成瘤情况.同时对肝脏标本进行组织病理学检查.结果:80只免疫小鼠中,A组肝细胞癌发生率为70%;B组肝细胞癌发生率仅为25%;C组肝癌发生率为65%;D组肝癌发生率为75%.B组与其它对照组比较有显著性差异(p＜0.05),其他各组比较无显著性意义.结论:转基因pAdBM5-mAFP-DC瘤苗免疫自然诱癌的C57BL/6J小鼠,能激发较强的抗肿瘤免疫反应,降低肝癌的发生率.     

Aging-like Spontaneous Epigenetic Silencing Facilitates Wnt Activation,Stemness, and BrafV600E-Induced Tumorigenesis

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mAFP基因转染树突状细胞免疫对小鼠诱发性肝癌发生的影响

目的:探讨用mAFP基因转染的树突状细胞(dendritic cells,DC)瘤苗免疫对小鼠诱发性肝癌发生的影响。方法:诱导、扩增C57BL/6J小鼠DC。将表达小鼠AFP基因(mAFP)的重组腺病毒转染DC。80只C57BL/6J雄性小鼠随机分为A、B、C、D组,每组20只。以单纯DC为A组;将表达mAFP基因的重组腺病毒转染DC(pAd-BM5-mAFP-DCs)为B组;表达mAFP基因的质粒DNA(pAdBM5-mAFP)为C组;以单纯PBS(磷酸缓冲液)注射为对照组D组。免疫方法:实验组在每只小鼠的左胁部注射5×105个细胞(0.1ml/次),连续免疫3天,以后每7天接种疫苗1次,继续免疫4次。正常对照组,仅注射0.1ml PBS。在接种免疫的同时,给以二乙基亚硝胺(DEN)、四氯化碳(CCl4)和乙醇联合诱癌。诱癌20周后处死小鼠,检查成瘤情况。同时对肝脏标本进行组织病理学检查。结果:80只免疫小鼠中,A组肝细胞癌发生率为70%;B组肝细胞癌发生率仅为25%;C组肝癌发生率为65%;D组肝癌发生率为75%。B组与其它对照组比较有显著性差异(p<0.05),其他各组比较无显著性意义。结论:转基因pAdBM5-mAFP-DC瘤苗免疫自然诱癌的C57BL/6J小鼠,能激发较强的抗肿瘤免疫反应,降低肝癌的发生率。     

The effect Akt2 deletion on tumor development in Pten(+/-) mice

The serine/threonine kinase Akt is frequently activated in human cancers and is considered an attractive therapeutic target. However, the relative contributions of the different Akt isoforms to tumorigenesis, and the effect of their deficiencies on cancer development are not well understood. We had previously shown that Akt1 deficiency is sufficient to markedly reduce the incidence of tumors in Pten(+/-) mice. Particularly, Akt1 deficiency inhibits endometrial carcinoma and prostate neoplasia in Pten(+/-) mice. Here, we analyzed the effect of Akt2 deficiency on the incidence of tumors in Pten(+/-) mice. Relative to Akt1, Akt2 deficiency had little-to-no effect on the incidence of prostate neoplasia, endometrial carcinoma, intestinal polyps and adrenal lesions in Pten(+/-) mice. However, Akt2 deficiency significantly decreased the incidence of thyroid tumors in Pten(+/-), which correlates with the relatively high level of Akt2 expression in the thyroid. Thus, unlike Akt1 deletion, Akt2 deletion is not sufficient to markedly inhibit tumorigenesis in Pten(+/-) mice in most tested tissues. The relatively small effect of Akt2 deletion on the inhibition of tumorigenesis in Pten(+/-) mice could be explained, in part, by an insufficient decrease in total Akt activity, due to the relatively lower Akt2 versus Akt1 expression, and relatively high blood insulin levels in Pten(+/-)Akt2(-/-) mice. The relatively high blood insulin levels in Pten(+/-)Akt2(-/-) mice may elevate the activity of Akt1, and possibly Akt3, thus, limiting the reduction of total Akt activity and preventing this activity from dropping to a threshold level required to inhibit tumorigenesis.     

神经和肿瘤发生

人体神经通过调控干细胞、驱动血管生成、调节免疫系统和影响微生物群启动肿瘤发生,轴突发生进一步促进早期肿瘤的生长.神经也是肿瘤微环境的重要组成部分,控制神经纤维和神经信号将成为新的肿瘤治疗策略,本文系统综述神经对肿瘤发生的影响.     

DADS对人结肠癌SW480细胞裸鼠致瘤的影响

目的探讨二烯丙基二硫（DADS）对人结肠癌SW480细胞裸鼠致瘤的影响。方法建立人结肠癌裸鼠移植瘤模型。15只实验裸鼠分为3组,每组5只。观察DADS对裸鼠致瘤的影响,并记录各组裸鼠及其皮下移植瘤的生长情况,绘制肿瘤生长曲线,计算肿瘤体积和肿瘤生长抑制率。光镜下观察移植瘤组织形态学改变,采用免疫组织化学法检测瘤组织内增殖细胞核抗原（PCNA）、p21WAF1蛋白表达情况,应用流式细胞术检测移植瘤细胞周期分布。结果 DADS能明显降低人结肠癌SW480细胞致瘤性,抑制移植瘤生长,降低肿瘤组织异型性,引起细胞周期G2/M阻滞,抑制PCNA蛋白表达,增强p21WAF1蛋白表达。结论 DADS可明显降低人结肠癌SW480细胞的致瘤性,抑制SW480细胞增殖,引起G2/M期阻滞,其可能与抑制PCNA蛋白表达、增强p21WAF1蛋白表达有关。     

Igf2 ligand dependency of Pten(+/-) developmental and tumour phenotypes in the mouse

The tumour suppressor PTEN is a key negative regulator of the PI3K-Akt pathway, and is frequently either reduced or lost in human tumours. Murine genetic studies have confirmed that reduction of Pten promotes tumourigenesis in multiple organs, and demonstrated dependency of tumour development on the activation of downstream components such as Akt. Insulin-like growth factors (IGFs) act via IGF1R to activate the PI3K-Akt pathway, and are commonly upregulated in cancer. A context-dependent interplay between IGFs and PTEN exists in normal tissue and tumours; increased IGF2 ligand supply induces Pten expression creating an autoregulatory negative feedback loop, whereas complete loss of PTEN may either cooperate with IGF overexpression in tumour promotion, or result in desensitisation to IGF ligand. However, it remains unknown whether neoplasia associated with Pten loss is dependent on upstream IGF ligand supply in vivo. We evaluated this by generation of Pten(+/-) mice with differing allelic dosage of Igf2, an imprinted gene encoding the potent embryonic and tumour growth factor Igf2. We show that biallelic Igf2 supply potentiates a previously unreported Pten(+/-) placental phenotype and results in strain-dependent cardiac hyperplasia and neonatal lethality. Importantly, we also show that the effects of Pten loss in vivo are modified by Igf2 supply, as lack of Igf2 results in extended survival and delayed tumour development while biallelic supply is associated with reduced lifespan and accelerated neoplasia in females. Furthermore, we demonstrate that reduction of PTEN protein to heterozygote levels in human MCF7 cells is associated with increased proliferation in response to IGF2, and does not result in desensitisation to IGF2 signalling. These data indicate that the effects of Pten loss at heterozygote levels commonly observed in human tumours are modified by Igf2 ligand, and emphasise the importance of the evaluation of upstream pathways in tumours with Pten loss.     

Skin abnormality in aged fyn-/- fak+/- mice

Focal adhesion kinase (FAK) is a novel non-receptor protein tyrosine kinase implicated in transducing signals from cell surface receptors. Its association with Fyn, a member of the Src family of tyrosine kinases, has been observed in cell lines. To examine in vivo the interaction between these two proteins, Fyn-deficient mice were bred with fak heterozygous mutants (Fak deficiency is embryonic lethal). A majority of animals with the double mutation (fyn-/- fak+/-) displayed a transient impairment in thymocyte development at four weeks of age. However, all of them developed skin abnormalities at the age of 8-12 months. The most prominent among abnormalities was a greatly increased number and size of sebaceous glands. Also, the epidermis was thickened and hyperkeratotic. These observations would suggest involvement of Fyn and FAK in keratinocyte differentiation.      

EPH受体与ephrin配体在肿瘤中的研究进展

Eph受体是已知最大的酪氨酸激酶受体家族,与ephrin配体结合产生双向信号在胚胎成形、神经轴突导向、血管发育中起着关键作用。最近一些基因缺失及体外血管形成实验表明EphB和ephrinB在胚胎血管分化及成人病理性血管形成中发挥重要作用,并且Eph和ephrin基因在各种肿瘤中不同程度的表达与肿瘤的恶性进展有关,如:侵袭力增强,更易于发生转移,血管化程度更明显等,由此而导致患者预后差。本文简要回顾了近来Eph受体家族与其配体在肿瘤发生方面的最新进展。