Early inflammatory changes in the skin of SENCAR and C57BL/6 mice following exposme to 12-O-tetradecanoylphorbol-13-acetat

Tumor-promoting phorbol esters are potent inflammatory agents.Inflammation has long been associated with carcinogenesis, particularlythe promotion. SENCAR mice have been bred for their sensitivityto the promotion of skin tumors by phorbol esters whereas C57BLl6mice have been shown to be resistant. When 12-O-tetradecawylphorbol-13acetate (TPA) was applied to the skin of SENCAR and CS7BL/6mice, SENCAR mice had a much more intense inflammatory responsethan the C57BL/6 animals. There was more edema formation atthe site of application and vascular permeability was also greatlyenhanced in the SENCAR strain. When samples of skin were examinedmicroscopically, a fulminant, acute inflammatory cellular infiltratewas observed in SENCAR mice. Very few inflammatory cells migratedinto the skin of C57BL/6 mice. At higher doses and multipleexposum to TPA there was a hyperplastic response of the keratinocytesin C57BL/6 mice, but it was less intense than in SENCAR mice.These data demonstrate that enhanced inflammatory resporms inTPA in the skin correlate with the sensitivity to the promotionof skin tumors by TPA.     

Src kinase induces tumor formation in the c-SRC C57BL/6 mouse

Src kinase has been linked as a causative agent in the progression of a number of cancers including colon, breast, lung and melanoma. Src protein and activity levels are increased in colorectal cancer and liver metastases arising secondary to colon cancer. However, although Src protein is increased in colon cancer as early as the adenomatous polyp stage, a role for Src in carcinogenesis has not been established. We developed the c-SRC transgenic mouse in the C57BL/6 strain to address the issue of carcinogenesis in cells with high levels of Src expression. The transgene was constructed with the human c-SRC gene downstream of the mouse metallothionein promoter to create zinc inducible gene expression. In these C57BL/6 mice, Src protein was increased in a number of tissues both with and without zinc induction. No additional carcinogenic agent was administered. After 20 months, mice were assessed for tumor development in the liver and GI tract, as well as other organs. Of the mice with the transgene, 15% developed tumors in the liver while no tumors were detected in wild type C57BL/6 mice. A further study was conducted by crossing c-SRC C57BL/6 mice with p21 nullizygous mice to determine the effect of oncogene expression combined with inactivation of the tumor suppressor gene, p21. Addition of the c-SRC transgene to the p21-/- background increased tumor formation almost 3-fold, while it increased metastasis 6-fold. The data from our study show, for the first time, that Src kinase may play a role in carcinogenesis.     

C57BL/6小鼠放射性心肺功能不全动物模型建立

目的 建立C57BL/6小鼠放射性心肺功能不全动物模型。方法 24只雄性C57BL/6小鼠随机分为对照组、照射组。照射组接受胸部局部单次20 Gy电子线照射,照后饲养6个月。超声心动检查心功能,血气分析检测血氧分压(PaO₂),Tunel染色法检测细胞凋亡,Masson染色法检测心肺纤维化。结果 照射组LVEF (68.60±10.92)%与对照组(81.75±8.79)%降低(P<0.01);照射组心脏凋亡指数(23.90±6.60)%比对照组(3.25±3.38)%增高(P<0.01);照射组心脏CVF (15.42±5.72)%比对照组(1.45±0.64)%增高(P<0.01)。照射组PaO₂(86.10±7.60) mmHg比对照组PaO₂(107.16±9.01) mmHg下降(P<0.01);照射组肺脏凋亡指数(27.90±8.94)%比对照组(2.50±3.55)%增高(P<0.01);照射组肺脏CVF (17.76±5.77)%比对照组(2.50±3.55)%增高(P<0.01)。结论 辐射使心肺凋亡纤维化重塑,进而导致心肺功能的下降,成功构建C57BL/6小鼠放射性心肺功能不全动物模型。     

Establishment of C57BL/6 mouse models with radiation-induced cardiopulmonary dysfunction

Objective To establish the C57BL/6 mouse models of radiation-induced cardiopulmonary dysfunction. Methods Twenty-four male C57BL/6 mice were randomly divided into the control and irradiation groups. Mice in the irradiation group were irradiated with 20 Gy electron beam and bred for 6 months after irradiation. Cardiac function was assessed using ultrasonography. The partial pressure of oxygen was detected by blood gas analysis. Cell apoptosis was observed by Tunel assay. Myocardial and pulmonary fibrosis was assessed by Masson staining. Results The LVEF in the irradiation group was (68.60±10.92)%, significantly less compared with (81.75±8.79)% in the control group (P< 0.01). The apoptotic index of heart in the irraiation group was (23.90±6.60)%, considerably higher than (3.25±3.38)% in the control group (P< 0.01). The CVF of heart in the irradiation group was (15.42±5.72)%, significantly higher than (1.45±0.64)% in the control group (P< 0.01). The PaO₂ level in the irradiation group was (86.10±7.60) mmHg, significantly lower compared with (107.16±9.01) mmHg in the control group (P< 0.01). The apoptotic index of lung in the irradiation group was (27.90±8.94)%, significantly higher than (2.50±3.55)% in the control group (P<0.01). The CVF of lung in the irradiation group was (17.76±5.77)%, remarkably higher than (2.50±3.55)% in the control group (P< 0.01). Conclusion Radiation can induce cardiopulmonary apotosis and fibrosis remodeling, which leads to cardiopulmonary dysfunction, suggesting the successful establishment of C57BL/6 mouse model of radiation-induced cardiopulmonary dysfunction.     

Tumor necrosis factor and interferon gamma inhibit the development of radiation-induced thymic lymphomas in C57BL/Ka mice

Recombinant tumor necrosis factor and/or gamma-interferon were injected into C57BL/Ka mice after completion of a whole body split dose irradiation, which usually induces thymic lymphomas in more than 90% of the animals. The survival and the incidence of thymic lymphomas were significantly reduced in the cytokine-injected irradiated mice. The protective effect was similar to that obtained by grafting normal bone marrow cells after irradiation. The mechanisms of lymphoma inhibition by TNF or IFN-gamma are discussed.     

Sensitivity to tumor promotion of SENCAR and C57BL/6J mice correlates with oxidative events and DNA damage

Significant differences in sensitivity to multistage carcinogenesishave been noted between mice that are sensitive (SENCAR) andresistant (C57BL/6J) to 12-O-tetradecanoyl-phorbol-13-acetate(TPA). However, the mechanism of this sensitivity has not yetbeen established. Recent studies from this laboratory have shownthat TPA significantly enhances formation of hydrogen peroxide(H₂O₂) and oxidized DNA bases in SENCAR mouse skin, as it increasesthe infiltration of polymorphonuclear leukocytes (PMNs), asquantitated by myeloperoxidase (MPO). In the studies reportedhere, we compared SENCAR and C57BL/6J mice with respect to TPA-mediatededema, hyperplasia, PMN infiltration, oxidant formation andoxidative DNA damage in mouse skin. Topical application of twoTPA doses (2x2–40 µg, 20 h apart) dose-dependentlyincreased PMN infiltration and oxidant formation in both mousestrains, which was consistent with TPA-induced morphologicalalterations (edema and hyperplasia). However, at low TPA doses(2–4 µg), the increases over controls in the SENCARmice were significantly greater (P < 0.01) than those inC57BL/6J mice. Comparison of the net values indicated that 4µg TPA enhanced PMN infiltration (MPO units/cm²) and oxidantformation (nmol H₂O₂/cm²) in SENCAR mice by 7.7- and 11-foldrespectively over those present in TPA-treated C57BL/6J mouseskin. At the same dose, TPA also significantly increased formationof thymidine glycol (dTG; 5.5-fold), 5-hydroxymethyl-2'-deoxy-uridine(HMdU; 4.9-fold) and 8-hydroxyl-2-deoxyguanosine (8-OHdG; 11.4-fold)in SENCAR mouse epidermis. Then, the levels of all three declined.In C57BL/6J mice, there were virtually no increases at 4 µgTPA, but their levels gradually increased with higher TPA dosesand reached maxima at 10 µg TPA for dTG (1.9-fold increase),at 20 µg TPA for 8-OHdG (6.0-fold), and at 30 µgTPA for HMdU (1.8-fold). We conclude that the TPA-mediated oxidativeevents and oxidative DNA modification by different doses ofTPA correlate with the promoting potencies of those doses inboth mouse strains. Therefore, they could be, at least in part,responsible for the strain-dependent sensitivity to tumor promotion.     

Cf-252 leukemogenesis in the C57BL mouse

Radiation-induced leukemia/lymphomas were induced in C57BL mice using four weekly acute 60Co fractionated irradiation exposures (to 188 cGy, or graded doses of low dose rate (LDR) Cf-252 irradiation given in fractionated exposure sessions at four weekly intervals. The acute 60Co radiation produced 84% thymic lymphomas with a median survival time (MST) of 162 days for mice developing tumors. Mice were exposed to Cf-252 n + gamma radiation in graded doses of 50, 62.5, 80, 112, and 188 cGy per week repeated 4X. Mice exposed to Cf-252 radiation developed thymic lymphomas on a much delayed time schedule. Mice irradiated at 50-80 cGy Cf-252 were killed after the 60Co induced thymoma mice had died to detect tumors. At Cf-252 doses of 112 or 188 rads 79 or 70% of mice, respectively, developed thymic lymphomas and had similar survival times which gave an estimated leukemogenesis RBEn of approximately 1.0-2.0. These studies show that for Cf-252 n + gamma radiation, compared to 60Co for leukemogenic efficiency, had a much longer latent period, and had a low RBE (1.0-2.0) at the large doses per fraction used in these studies. Under the experimental fractionated conditions tested, Cf-252 neutrons were leukemogenic, but only slightly more so than fractionated 60Co.     

1,2-Dimethylhydrazine-induced nuclear aberrations in A/J and C57BL/6J mouse colonic crypts

A single exposure to 1,2-dimethylhydrazine [(DMH) CAS: 540-73-8] produces several forms of aberrant nuclei in the crypts of the murine colon. The frequency of nuclear aberrations (NAs) was examined in the distal colonic crypts in DMH-sensitive A/J mice and relatively DMH-resistant C57BL/6J mice before and after a single exposure to DMH. NAs, mitotic figures, and crypt column heights were scored for all animals as a function of time following administration of DMH. In both strains there was a significant increase in the absolute and relative frequency of NAs by 12 hours, with a corresponding drop and subsequent overshoot in the mitotic index by 48 hours after DMH. The temporal changes in crypt column height correlate closely with the temporal changes in frequency of NAs in both strains. The results showed that both inbred strains respond to acute DMH exposure in a similar and parallel fashion over time. It was concluded that the NA index assay is a sensitive method for detecting early DMH exposure. However, this assay does not relate to ultimate outcome after chronic DMH exposure and should not be used as a predictor of eventual neoplastic transformation of colonic mucosa with this carcinogen.     

Inheritance of susceptibility to phototumorigenesis and persistent hyperplasia in F1 hybrids between SENCAR mice and BALB/c or C57BL/6 mice

SENCAR mice are selectively bred for hypersusceptibility to two-stage chemical skin carcinogenesis. They are also hypersusceptible to UV radiation tumorigenesis with single high-dose, but not chronic low-dose, exposures. In addition, SENCAR mice exhibit an exaggerated and persistent epidermal hyperplasia (due to sustained proliferation of the basal cells) in response to UV-induced tissue damage. In the present study, we have examined the inheritance of susceptibility to both phototumorigenesis and persistent hyperplasia in the F1 offspring of SENCAR mice crossed with either of two inbred strains (BALB/c or C57BL/6) which are relatively resistant to phototumorigenesis. A total of 428 mice from the parental strains and reciprocal F1 crosses were given a single high dose (8.64 x 10(4) J/m2) of UV radiation (FS40 sunlamps) which causes persistent hyperplasia and tumorigenesis in many SENCAR, but no BALB/c or C57BL/6, mice. F1 hybrids between SENCAR and C57BL/6 mice did not develop persistent hyperplasia or skin tumors, which indicates that susceptibility to both traits is completely recessive to the C57BL/6 genotype. In contrast, F1 hybrids between SENCAR and BALB/c mice developed both persistent hyperplasia and skin tumors, although at a much lower incidence than the SENCAR mice, indicating that susceptibility to both traits is only partially (incompletely) recessive to the BALB/c genotype. Thus, in either F1 cross, susceptibility to phototumorigenesis decreased in parallel with persistent hyperplasia. These results are consistent with the hypothesis that the two characteristics are mechanistically related.     

Ochratoxin A carcinogenesis in the (C57BL/6J X C3H)F1 mouse

The potential carcinogenic effects of the mycotoxin ochratoxin A [(OA); CAS: 303-47-9] were assessed in a 24-month feeding study in male and female (C57BL/6J X C3H)F1 (B6C3F1) mice. The mice were assigned to 3 groups of 50 males and 50 females each; group 1 mice were the controls, group 2 mice were fed 1 ppm OA, and group 3 mice were fed 40 ppm OA. Renal neoplasms, both carcinomas and adenomas, were found only in male mice of the 40-ppm dose group. Fourteen of 49 animals that survived at least 20 months had neoplasms morphologically consistent with renal carcinoma. Renal adenomas were present in some of these mice and in other 40-ppm-group males, making a total of 26 mice with renal adenomas. All male mice of the 40-ppm dose group had nephropathy characterized by varying degrees of renal tubular dilation, attenuation and hyperplasia of lining epithelium, and proliferation of regenerative tubules. Females of the 40-ppm dose group had similar but less severe renal changes but no carcinomas or adenomas. Compound-related renal lesions were absent in the 1-ppm dose group. The incidence of hepatocellular neoplasms was slightly increased in male and female mice fed diets containing OA. These results indicate that OA is a renal carcinogen in male B6C3F1 mice and a hepatic carcinogen in female mice of this strain.     

Ras mutations in methyiclofenapate-induced B6C3F1 and C57BL/1OJ mouse liver tumours

The majority of genotoxic carcinogen-induced liver tumours ofthe sensitive B6C3F1 mouse contain activated H-ras oncogenes.Such mutations also occur in hepatocarcinogenesis resistantstrains. In order to determine whether this is true of non-genotoxiccarcinogen-induced tumours, liver tumours induced in B6C3F1and C57BL/10J mice by methylclofena pate (MCP) were compared.Polymerase chain reaction (PCR) analysis revealed H-ras codon61 mutations in 11/46 B6C3F1 and 4/31 C57BL/10J liver tumours.The nude mouse tumorigenicity (NMT) assay was used to analysetumours without codon 61 mutations. Of the 12 B6C3F1 liver tumourDNAs subjected to this assay, one contained a H-ras codon 117mutation. Further PCR analysis on frozen tumour samples (46B6C3F1 and 15 C57BL/10J) revealed no codon 12 mutations; oneadditional codon 117 mutation was identified in a B6C3F1 tumour.Overall, then, H-ras codon 61 mutations were detected in MCP-inducedB6C3F1 tumours less frequently than in genotoxin-induced tumours.Two B6C3F1 tumours contained codon 117 mutations similar tothose previously found in tumours induced by ciprofibrate, furanand furfural, and in at least one spontaneous tumour. Ras mutationswere also detected in some C57BL/10J tumours, providing furtherevidence that ras oncogenes can participate in hepatocarcinogenesisin resistant mice.     

C57BL/6小鼠的血循环DNA的定量研究

目的探讨循环DNA的定量检测在荷瘤C57BL/6小鼠中的应用价值.方法以异位接种法在C57BL/6小鼠中建立B16黑色素瘤肝转移模型,以"微量基因组抽提试剂盒"抽提血清DNA,用SYBR Green I斑点荧光染色法对DNA进行定量.结果在正常小鼠中,血循环DNA为(62.4±25.52)ng/mL、荷瘤伴有肝转移小鼠为(241±73.7)ng/mL(P＜0.01);小鼠的血循环DNA水平与小鼠肝转移的分期相关,Ⅰ期、Ⅱ期肝转移小鼠分别为(131.11±54.32)ng/mL和(170±10.96)ng/mL,Ⅲ期、Ⅳ期小鼠为(235±85.54)ng/mL和(271±65.76)ng/mL.用健脾理气中药抑制肿瘤生长和转移的同时,荷瘤小鼠血循环DNA也同步下降.结论循环DNA定量检测能客观反应小鼠荷瘤程度,并能动态反应药物的疗效,是一具有应用前景的肿瘤标志物.     

C57BR/cdJ hepatocarcinogen susceptibility genes act cell-autonomously in C57BR/cdJ<-->C57BL/6J chimeras

Female C57BR/cdJ (BR) mice are unusually susceptible to spontaneous and chemically induced hepatocarcinogenesis relative to females of other inbred strains, in part because they are insensitive to the inhibitory effects of ovarian hormones on liver tumor development; BR males are intermediate among strains in their sensitivity. C57BL/6J (B6) male and female mice are relatively resistant among inbred strains. Linkage analysis of crosses between BR and resistant B6 mice identified two loci, on Chromosomes 17 and 1, that accounted for the high susceptibility of BR mice to hepatocarcinogenesis. To determine whether the increased susceptibility of BR relative to B6 mice is intrinsic to the target hepatocytes or is the result of local or systemic differences in milieu, we determined the strain of origin of tumors that arose in BR<-->B6 aggregation chimeras. Chimeras were treated at 12 days of age with N,N-diethylnitrosamine, and individual tumors were dissected from 15 males at 32 weeks and from 7 females at 50 weeks of age. DNA was prepared from each tumor, and quantitative PCR assays were used to determine the strain of origin for each tumor. The overall contribution of each strain to non-neoplastic liver was determined using the PCR assay and through analysis of the relative amount of glucose phosphate isomerase activity associated with the BR and B6 electrophoretic variants; the median contribution of B6 cells to non-neoplastic liver was 50%. A majority (91%) of the 230 tumors analyzed from both sexes was derived from the BR donor, indicating that the net overall effect of BR susceptibility genes is cell autonomous.     

Increased invasion and spontaneous metastasis of BL6 melanoma with inhibition of the desmoplastic response in C57 BL/6 mice

BL6 melanoma cells injected s.c. in 18-month C57 BL/6 mice elicit a markedly fibrotic response similar in myofibroblast and collagen composition to that characterizing the desmoplastic response of human breast carcinoma. This host response can be quantitated by measuring hydroxyproline (total collagen) and incorporation of i.p.-injected [14C]proline into collagenase-sensitive protein (new collagen synthesis). Inhibition (70%) of the desmoplastic response can be achieved by daily injections of L-3,4-dehydroproline. Inhibiting the response in this manner promotes local invasion of tumor and increases the incidence of spontaneous pulmonary metastasis. 10(5) BL6 melanoma cells produce tumor nodules with a mean diameter of 1.5 +/- 0.5 cm and mean collagen content of 36 +/- 15 mg/g wet tissue at 4 weeks and 10% incidence of pulmonary metastasis at 7 weeks. L-3,4-dehydroproline produces nodules with a mean diameter of 2.3 +/- 0.5 cm and mean collagen content of 12 +/- 2 mg/g with a 40% incidence of metastasis. L-3,4-dehydroproline exerts a selective effect on myofibroblast collagen synthesis in vitro and no effect on [3H]thymidine uptake, doubling time, and viability of BL6 cells and myofibroblasts. Furthermore, this drug exerts no effect on BL6 invasion and metastasis in 6-week C57 BL/6 mice, hosts which exhibit a negligible desmoplastic response.     

Characterization of C57BL/6 plasmacytomas lacking a c-myc translocation

BALB/c peritoneal plasmacytomas induced by a variety of agents are invariably associated with a c-myc translocation. In contrast, naturally arising bone marrow plasma cell tumors in C57BL/KaLwRij mice lack this translocation. This difference has led to the suggestion that these are 2 fundamentally different plasma cell diseases. Herein, we have analyzed 2 rare C57BL/6 peritoneal plasmacytomas in terms of characteristics associated with the bone marrow–derived lines. Like the bone marrow lines, these peritoneal plasmacytomas do not exhibit c-myc translocations, indicating that c- myc translocation is not an obligatory event in the development of all murine extramedullary plasmacytomas. However, myc is dysregulated at the mRNA level, indicating that myc over-expression may be fundamental to most plasma cell diseases but that dysregulation can occur by alternative mechanisms possibly reflecting different genetic backgrounds. Int. J. Cancer 72:892–897, 1997. Published 1997 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

C57BL/6小鼠微小残留白血病模型的建立

目的 探讨构建C57BL/6小鼠FBL-3微小残留白血病(MRL)模型的方法.方法 将5×106个FBL-3红白血病细胞经尾静脉接种至C57 BL/6小鼠,接种后第3天经尾静脉注射不同剂量环磷酰胺(CTX),观察小鼠生存时间与药物剂量间的关系;根据白血病小鼠生存时间与CTX剂量和与接种FBL-3细胞数量的关系,确定构建小鼠MRL模型所需的化疗药物剂量.结果 C57BL/6白血病小鼠对CTX敏感,随CTX剂量增加白血病小鼠的生存时间逐渐延长,药物剂量与生存时间有较好的回归关系.移植生物试验显示,接种500个FBL-3细胞的小鼠生存时间与接受100 mg·kg-1 CTX化疗白血病小鼠相当.结论每只C57BL/6小鼠经尾静脉接种5×106个FBL-3细胞3d后给予100 mg·kg-1 CTX化疗可以建立MRL动物模型.