E2f3 in tumor macrophages promotes lung metastasis.

The Rb-E2F axis is an important pathway involved in cell-cycle control that is deregulated in a number of cancers. E2f transcription factors have distinct roles in the control of cell proliferation, cell survival and differentiation in a variety of tissues. We have previously shown that E2fs are important downstream targets of a CSF-1 signaling cascade involved in myeloid development. In cancer, tumor-associated macrophages (TAMs) are recruited to the tumor stroma in response to cytokines secreted by tumor cells, and are believed to facilitate tumor cell invasion and metastasis. Using the MMTV-Polyoma Middle T antigen (PyMT) mouse model of human ductal carcinoma, we show that the specific ablation of E2f3 in TAMs, but not in tumor epithelial cells, attenuates lung metastasis without affecting primary tumor growth. Histological analysis and gene expression profiling suggest that E2f3 does not impact the proliferation or survival of TAMs, but rather controls a novel gene expression signature associated with cytoskeleton rearrangements, cell migration and adhesion. This E2f3 TAM gene expression signature was sufficient to predict cancer recurrence and overall survival of estrogen receptor (ER)-positive breast cancer patients. Interestingly, we find that E2f3b but not E2f3a levels are elevated in TAMs from PyMT mammary glands relative to controls, suggesting a differential role for these isoforms in metastasis. In summary, these findings identify E2f3 as a key transcription factor in TAMs, which influences the tumor microenvironment and tumor cell metastasis.

Superficial radial nerve damage due to Kirschner wiring of the radius.

For displaced fractures of the radius, the use of Kirschner wires (K Wires) is accepted practice either alone or to supplement external fixation. Complications related to K wires include infection, migration and damage to tendons and nerves. We set out to investigate to incidence of superficial radial nerve damage due to radial styloid K wires. Injury to the sensory branch of the superficial radial nerve was seen in eight (20%) out of the 40 patients. K wiring is a popular technique to help maintain anatomic reduction of distal radial fractures. It has the advantage of being a semi-closed procedure, which is simple to perform. However, the morbidity of nerve damage is often underestimated and can be avoided.

Inhibition of benzo[a]pyrene- and cyclophoshamide-induced mutagenicity by Cinnamomum cassia.

Cinnamomum cassia is used as a flavoring spice with some established medicinal properties. In this study, we evaluated the antimutagenic effect of C. cassia against two mutagens, viz. benzo[a]pyrene (B[a]P) and cyclophosphamide (CP). The antimutagenic properties of C. cassia were examined by the Ames test. In vivo chromosomal aberration (CA) and micronuclei tests were also employed to assess the antimutagenic effect of C. cassia in mice after pretreatment with the extract orally for seven consecutive days. To elucidate the mechanism by which C. cassia exerts its antimutagenic effect, certain key enzymes involved in bioactivation and detoxification processes were also investigated. Changes in liver cytochrome P450 (Cyt P450), glutathione content (GSH), glutathione S-transferase (GST), glutathione reductase (GR), and glutathione peroxidase (GPX) were evaluated in pretreated animals. It was observed in the Ames test, bone marrow chromosomal aberration assay, and micronucleus test that C. cassia exerted significant antimutagenic effects against B[a]P and CP in animals treated with the plant extract. C. cassia pretreatment decreased Cyt P450 content but increased GSH content and the activity of glutathione-dependent antioxidant enzymes, viz. GST, GR, and GPX. The present findings demonstrate that the antimutagenic potential of C. cassia could be attributed to its modulatory effect on the xenobiotic bioactivation and detoxification processes.

Nitroglycerin: a NO donor inhibits TPA-mediated tumor promotion in murine skin.

Nitroglycerin (GTN), a nitric oxide (NO) generating vasodilator has been used in the present study to assess the role of NO during tumor promotion in murine skin. Administration of GTN to 12-O tetradecanoyl phorbol 13-acetate (TPA)-treated mice resulted in a dose-dependent inhibition in the level of glutathione and the activity of antioxidant enzymes by approximately 16-40% of acetone-treated control. We also observed that GTN application led to a significant reduction in the ornithine decarboxylase (ODC) activity and decreased the rate of [3H]thymidine incorporation into epidermal DNA when compared with the acetone-treated control (P < 0.001). Treatment of DMBA-initiated TPA-promoted mice with GTN increased the latency period, decreased the tumor incidence by 32% and there was a 2-fold decrease in tumor yield (tumor/mouse) as compared with the TPA (alone)-treated group by 20 weeks. From these data, it can be concluded that NO can abrogate the toxic and tumor promoting effects of TPA and GTN can be used as a chemopreventive agent to inhibit tumorigenesis in murine skin.

Inhibitory effect of Emblica officinalis on the in vivo clastogenicity of benzo[a]pyrene and cyclophosphamide in mice.

Benzo[a]pyrene (B[a]P) and cyclophosphamide (CP) are potent carcinogens/mutagens. Effect of Emblica officinalis extract administration on the in vivo genotoxicity of B[a]P and CP was studied using bone marrow chromosomal aberration and micronucleus induction tests in mice. Three doses (50, 250 and 500 mg/kg body weight) of the plant extract were administered orally for 7 consecutive days prior to the administration of single dose of mutagens (B[a]P 125 mg/kg oral; CP 40 mg/kg i.p.). It was found that administration of 250 and 500 mg/kg of E. officinalis extract significantly inhibited the genotoxicity of B[a]P as well as CP in both the assay systems. Administration of 50 mg/kg of the plant extract had no inhibitory effect. Vitamin C, a major constituent of E. officinalis when administered at dose level of 9 mg/kg b.w. (the approximate estimated amount present in the highest dose of plant extract, i.e. 500 mg) for 7 days did inhibit chromosomal aberrations and micronuclei induction, but not in a significant manner. Effect of administration of the abovementioned effective doses (250 and 500 mg/kg oral for 7 days) of plant extract and vitamin C (9 mg/kg oral for 7 days) on the hepatic activation and detoxification enzymes was also studied. Significant induction in the levels of glutathione content (GSH) and of antioxidant and detoxification enzymes viz., glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione-S transferase (GST) resulted from plant extract treatment to animals. On the other hand, cytochrome P 450 level was significantly decreased in the plant-extract-treated animals. There was no significant change in cytochrome P 450, GSH contents and activities of enzymes on treatment with vitamin C. The data indicate that the possible mechanism of inhibition by plant extract is mediated by its modulatory effect on hepatic activation and disposition processes.

In vitro inhibition of carcinogen-induced mutagenicity by Cassia occidentalis and Emblica officinalis.

Aqueous extracts of Cassia occidentalis Linn. (Leguminoceae) and Emblica officinalis Gaertn. (Euphorbiaceae) were screened for effectiveness in inhibiting mutagenicity of aflatoxin B1 (AFB1) and benzo[a]pyrene (B[a]P) in the Ames test. Antimutagenicity was evaluated using Salmonella typhimurium strains TA 98 and TA 100. In the assay, metabolic activation of AFB1 (0.5 microg/plate) and B[a]P (1 microg/plate) was mediated by rat liver S9 preparation. Although both plants inhibited mutagenicity, E. officinalis had more inhibitory effect than C. occidentalis. Their action is possibly mediated through interactions with microsomal activating enzymes. Their inhibitory action on chromosomal aberrations together with present results suggest that these plants have potent antimutagenic and anticarcinogenic activities against mutagens requiring metabolic activation.

Protective effect of Cassia occidentalis extract on chemical-induced chromosomal aberrations in mice.

This study was conducted to determine the antimutagenic potential of aqueous extract of Cassia occidentalis against the chromosomal aberrations (CA) produced in vivo by benzo[a]pyrene (B[a]P) and cyclophosphamide (CP) in mice. Animals (male mice) were treated with three doses of plant extract (50 mg/kg, 250 mg/kg and 500 mg/kg) for 7 days prior to the administration of single dose of mutagens (B[a]P 125 mg/kg oral; CP 40 mg/kg i.p.). The results indicated that C. occidentalis was not genotoxic per se and exerted no other toxic signs and symptoms in treated animals. The chromosomal aberrations produced by B[a]P and CP were significantly reduced (p < 0.001) by C. occidentalis pre-treatment. Furthermore, animals treated with plant extract showed a reduced level of cytochrome P 450 (Cyt P 450) and elevated levels of glutathione S-transferase (GST) activity and glutathione content in the liver. It seems that C. occidentalis exerts its antimutagenic activity by modulating the xenobiotic activation and detoxification mechanisms.

Evidence that ferric nitrilotriacetate mediates oxidative stress by down-regulating DT-diaphorase activity: implications for carcinogenesis.

Ferric nitrilotriacetate (Fe-NTA) is a known complete renal carcinogen as well as renal and hepatic tumor promoter, which acts by generating oxidative stress in the tissue. However, the mechanism by which it generates this stress is not fully understood. In this study, we show that Fe-NTA down-regulates hepatic and renal quinone reductase (QR) activity dose dependently. The maximum decrease in the activity of QR was observed at 12 h in the liver and 6 h in the kidney following Fe-NTA treatment. However, at all other time points studied, QR activity was reduced. In addition, a parallel increase in protein carbonyl content, a sensitive indicator of tissue oxidative stress was observed both in the liver and kidney. The pretreatment of animals with antioxidants, butylated hydroxyanisole and butylated hydroxytoluene, prevented the observed inhibition in the activity of QR and enhanced the formation of protein carbonyl in both organs. These studies suggest that Fe-NTA-mediated generation of oxidant free radicals down-regulates QR activity which may be responsible, at least in part, for the observed renal and hepatic injury and carcinogenic properties of Fe-NTA.