Difference in carcinogenicities of two different vapor grown carbon fibers with different physicochemical characteristics induced by intratracheal instillation in rats

BACKGROUND

Carbon fibers are high aspect ratio structures with diameters on the submicron scale. Vapor grown carbon fibers are contained within multi-walled carbon tubes, with VGCF™-H commonly applied as a conductive additive in lithium-ion batteries. However, several multi-walled carbon fibers, including MWNT-7, have been reported to induce lung carcinogenicity in rats. This study investigated the carcinogenic potential of VGCF™-H fibers in F344 rats of both sexes with the vapor grown carbon fibers VGCF™-H and MWNT-7 over 2 years. The carbon fibers were administered to rats by intratracheal instillation at doses of 0, 0.016, 0.08, and 0.4 mg/kg (total doses of 0, 0.128, 0.64, and 3.2 mg/kg) once per week for eight weeks and the rats were observed for up to 2 years after the first instillation.

RESULTS

Histopathological examination showed the induction of malignant mesothelioma on the pleural cavity with dose-dependent increases observed at 0, 0.128, 0.64, and 3.2 mg/kg in rats of both sexes that were exposed to MWNT-7. On the other hand, only two cases of pleural malignant mesothelioma were observed in the VGCF™-H groups; both rats that received 3.2 mg/kg in male. The animals in the MWNT-7 groups either died or became moribund earlier than those in the VGCF™-H groups, which is thought related to the development of malignant mesothelioma. The survival rates were higher in the VGCF™-H group, and more carbon fibers were observed in the pleural lavage fluid (PLF) of the MWNT-7 groups. These results suggest that malignant mesothelioma is related to the transfer of carbon fibers into the pleural cavity.

CONCLUSIONS

The intratracheal instillation of MWNT-7 clearly led to carcinogenicity in both male and female rats at all doses. The equivocal evidence for carcinogenic potential that was observed in male rats exposed to VGCF™-H was not seen in the females. The differences in the carcinogenicities of the two types of carbon fibers are thought due to differences in the number of carbon fibers reaching the pleural cavity. The results indicate that the carcinogenic activity of VGCF™-H is lower than that of MWNT-7.

Lung toxicity of a vapor-grown carbon fiber in comparison with a multi-walled carbon nanotube in F344 rats

Carbon fibers have excellent physicochemical and electrical properties. Vapor-grown carbon fibers are a type of carbon fibers that have a multi-walled carbon tube structure with a high aspect ratio. The representative vapor-grown carbon fiber, VGCF^TM-H, is extremely strong and stable and has superior thermal and electrical conductivity. Because some high-aspect-ratio multi-walled carbon nanotubes (MWCNTs) have been reported to have toxic and carcinogenic effects in the lungs of rodents, we performed a 13-week lung toxicity study using VGCF^TM-H in comparison with one of MWCNTs, MWNT-7, in rats. Male and female F344 rats were intratracheally administered VGCF^TM-H at doses of 0.2, 0.4, and 0.8 mg/kg bw or MWNT-7 at doses of 0.4 and 0.8 mg/kg bw once a week for 8 weeks and then up to week 13 without treatment. The lung burden was equivalent in the VGCF^TM-H and MWNT-7 groups; however, the lung weight had increased and the inflammatory and biochemical parameters in the broncho-alveolar lavage fluid and histopathological parameters, including inflammatory cell infiltration, alveolar type II cells proliferation, alveolar fibrosis, pleural fibrosis, lung mesothelium proliferation, and diaphragm fibrosis, were milder in the VGCF^TM-H group than in the MWNT-7 group. In addition, the proliferating cell nuclear antigen (PCNA)-positive index in the visceral and pleural mesothelium was significantly higher in the MWNT-7 group than in the controls, but not in the VGCF^TM-H group. Thus, the results of this study indicate that the lung and pleural toxicities of VGCF^TM-H were less than those of MWNT-7.

Dasatinib-induced Nonspecific Interstitial Pneumonia That Developed 7 Years after the Initiation of Dasatinib

We report the case of a 56-year-old man with chronic myeloid leukemia (CML) who developed dasatinib-induced interstitial lung disease (ILD) 7 years after starting dasatinib, a BCR-ABL1 inhibitor. The patient presented with dyspnea. Chest imaging showed diffuse ground-glass opacities. A surgical lung biopsy showed cellular non-specific interstitial pneumonia (NSIP). Corticosteroid treatment ameliorated his condition. Bosutinib, another BCR-ABL1 inhibitor, was successfully re-instituted. The present case and relevant literature suggest that dasatinib-induced ILD can present as NSIP after an extended period, responds to corticosteroids, and is amenable to re-challenge at a lower-dose or with alternative BCR-ABL1 inhibitors.

Comparison of the effects of multiwall carbon nanotubes on the epithelial cells and macrophages

Effects of two kinds of multiwall carbon nanotubes (MWCNTs) on cells were examined. The effects of MWNT-7, which has been reported to be carcinogenic, and MWCNT-B, whose toxicity is unclear, were examined in both epithelial cells and macrophages. Human lung carcinoma A549 cells were used as representative epithelial cells and differentiated human monocyte THP-1 cells, as well as rat pulmonary macrophages NR8383, were employed to examine possible harmful effects of the MWCNTs. The MWCNTs induced the production of chemokines such as interleukin-8 (IL-8). MWCNTs were found to more strongly affect macrophages than epithelial cells. In addition, the toxicity was more pronounced in the MWNT-7 exposed cells than in those exposed to MWCNT-B. Cytochalasin D and amiloride treatment of differentiated THP-1 cells reduced cell-associated MWCNTs and IL-8 induction. To confirm these cellular influences in vivo, intratracheal administration of each type of MWCNT was performed by pharyngeal aspiration in the mouse lung. Analysis of bronchoalveolar lavage fluid (BALF) showed increase of inflammatory monocyte in MWNT-7 exposed animals at 1week after. In addition, neutrophils in the BALF were also significantly increased MWNT-7 exposed animals at 1 week and 1 month after. Aspiration of MWNT-7 caused formation of granulomas in the lung. Formation of the granulomas was not observed in the case of MWCNT-B. These results suggest that cellular uptake of the MWCNTs by phagocytosis and chemokine induction is important aspects of their toxicity.

Effect of iron overload from multi walled carbon nanotubes on neutrophil-like differentiated HL-60 cells

Multi walled carbon nanotubes (MWCNTs) are one of the most intensively explored nanomaterials because of their unique physical and chemical properties. Due to the widespread use of MWCNTs, it is important to investigate their effects on human health. The precise mechanism of MWCNT toxicity has not been fully elucidated. The present study was designed to examine the mechanisms of MWCNT toxicity toward human promyelocytic leukemia HL-60 cells. First, we found that MWCNTs decreased the viability of neutrophil-like differentiated HL-60 cells but not undifferentiated HL-60 cells. Because neutrophil-like differentiated HL-60 cells exhibit enhanced phagocytic activity, the cytotoxicity of MWCNTs is dependent on the intracellularly localized MWCNTs. Next, we revealed that the cytotoxicity of MWCNTs is correlated with the intracellular accumulation of iron that is released from the engulfed MWCNTs in an acidic lysosomal environment. The intracellular accumulation of iron was repressed by treatment with cytochalasin D, a phagocytosis inhibitor. In addition, our results indicated that iron overload enhanced the release of interleukin-8 (IL-8), a chemokine that activates neutrophils, and subsequently elevated intracellular calcium concentration ([Ca²⁺]_i). Finally, we found that the sustained [Ca²⁺]_i elevation resulted in the loss of mitochondrial membrane potential and the increase of caspase-3 activity, thereby inducing apoptotic cell death. These findings suggest that the iron overload caused by engulfed MWCNTs results in the increase of IL-8 production and the elevation of [Ca²⁺]_i, thereby activating the mitochondria-mediated apoptotic pathway.

Sudden termination of G-CSF injection leads to apoptosis of a large proportion of increased granulocytes

The effectiveness of granulocyte colony-stimulating factor (G-CSF) for granulocytopenia has been widely recognized. However, although granulocyte counts rapidly increase after a few injection of G-CSF, a large proportion of the increased granulocytes disappear from peripheral blood within a few days following G-CSF withdrawal. Where do they go? In this report, the answer can be seen at a glance. Using MitoCapture and a CCD camera-equipped fluorescence microscope, we succeeded in demonstrating that G-CSF withdrawal induced loss of mitochondrial membrane potential, i.e., an early stage of apoptosis, in human peripheral granulocytes increased by G-CSF.

Radiation-induced apoptosis of human peripheral T cells: analyses with cDNA expression arrays and mitochondrial membrane potential assay

We examined sequential changes in post-irradiated peripheral blood T cells taken from normal volunteers, by using targeted Atlas cDNA Expression Arrays and mitochondrial membrane potential assay. At 1 and 3 hours after 5 Gy irradiation, changes of gene expression were examined by targeted Atlas cDNA Expression Arrays using Apoptosis Array. The Atlas Human Apoptosis Array includes 205 key genes that are known to control apoptosis, including extracellular and cytoplasmic effectors. Concerning Fas, no significant changes of spot intensities were identified between irradiated T cells and non-irradiated ones at both 1 h and 3 h after 5 Gy irradiation. Caspase families, including caspases 9 and 3 also showed no changes between these two groups. An apoptosis regulator bclw showed a remarkable decrease in irradiated T cells. These results suggested that irradiation induced direct apoptosis of T cells by changing the membrane potential of mitochondria. Using a CCD camera-equipped fluorescence microscope and MitoCapture, a mitochondrial membrane potential indicator, we demonstrated 5 Gy radiation induced loss of membrane potential, i.e., an early stage of apoptosis, in human peripheral blood T cells at 10 hours after irradiation.

Toremifene-induced fatty liver and NASH in breast cancer patients with breast-conservation treatment

We have described fatty liver, diagnosed by computed tomography scanning (CT) in more than 30% of patients with breast cancer who received tamoxifen. Therefore, it is urgent to elucidate the frequency and the degree of fatty liver induced by toremifene, an analogue of tamoxifen, which is also used in breast cancer. We enrolled 52 breast cancer patients who were treated with breast-conservation treatment and administered oral toremifene for 3-5 years as adjuvant endocrine therapy. We evaluated the degree of fatty liver by abdominal CT performed annually. CT demonstrated toremifene-induced fatty liver in four (7.7%) of 52 breast cancer patients. Toremifene-induced fatty liver did not correlate with abnormal levels of AST, ALT, GGT or total cholesterol. One patient who demonstrated moderate fatty liver by CT was histologically diagnosed as non-alcoholic steatohepatitis (NASH) by liver biopsy. The incidence of toremifene-induced fatty liver was significantly lower than that induced by tamoxifen. Accordingly, in terms of fatty liver and NASH, toremifene is considered to be more appropriate agent than tamoxifen. Though toremifene is less likely to induce fatty liver, the possibility remains that toremifene-induced steatohepatitis occurs. Because the diagnosis of fatty liver or NASH can be easily missed if only a blood test is performed, it is necessary to screen fatty liver by annual CT examination for patients who receive an antiestrogen agent.

Breast-conservation treatment for patients with ductal carcinoma in situ

Fourteen cases with symptomatic ductal carcinoma in situ (DCIS) were treated with breast-conservation treatment intensified with endocrine therapy. Nine of 14 patients with palpable mass had tumor detected on mammography. CT, ultrasonography, and MRI were able to detect linear and/or spotty lesion or enhancement suggesting DCIS. Whereas these findings were not particular to DCIS, the combination of these modalities would be useful in deciding the extent of resection for DCIS. There was no patient selection for breast-conservation treatment in our department. All patients received tangential and boost radiation, and were treated with endocrine therapy using anti-estrogen drugs. The reason that nine cases had close margins (<5 mm) might be on account of the treatment including lumpectomy with 1 cm of surgical margin. In spite of their margin status, no local or systemic failure was experienced, and the cosmetic results of most patients were rated as excellent or good. Therefore, our breast-conservation treatment intensified with systemic therapy is thought to be adequate for patients with symptomatic DCIS. Six of eight cases who received preoperative treatment containing endocrine therapy with or without CAF chemotherapy showed a decrease in tumor size. Preoperative treatment may effect the microinvasion and/or breast tissue surrounding a DCIS tumor.

Unrecognized hepatic steatosis and non-alcoholic steatohepatitis in adjuvant tamoxifen for breast cancer patients

Adjuvant tamoxifen has become the treatment of choice against estrogen receptor-positive breast cancer. Adverse effects are rarely observed and since symptoms of hepatic steatosis, non-alcoholic steatohepatitis and cirrhosis are usually negligible, such effects are not well characterized despite large cohort studies of adjuvant tamoxifen. This issue remains to be systematically studied. The present study consisted of 136 breast cancer patients treated with or without tamoxifen. Patients had laboratory tests once each month and underwent abdominal computed tomography (CT) annually for 5 years. The extent of hepatic steatosis was assessed by CT as the liver/spleen ratio. While receiving adjuvant tamoxifen, 40 of 105 patients developed hepatic steatosis (liver/spleen ratio <0.9) without obvious changes in body mass index. Twenty-one had a liver spleen ratio of <0.5, whereas none of the 31 patients treated without tamoxifen had a ratio <0.9 or <0.5 (p<0.0001 and p<0.0001, respectively). Hepatic steatosis was recognized in 35 of the 40 patients within the first 2 years of receiving adjuvant tamoxifen and 21 of the 40 had increased transaminase levels. Liver biopsy revealed NASH in 6 of 7 patients among the 21 with a liver/spleen ratio of <0.5. A subset of individuals given adjuvant tamoxifen developed progressive hepatic steatosis without significant changes in the body mass index. We suggest a liver/spleen ratio of <0.5 as a criterion upon which liver biopsy should be recommended since NASH frequently occurred in such patients.

Effect of multidisciplinary treatment with high dose rate intraluminal brachytherapy on survival in patients with unresectable esophageal cancer

BACKGROUND

Since carcinoma of the esophagus is usually diagnosed at an advanced stage, many cases of esophageal cancer are beyond possible radical resection and only palliative treatment can be performed in such cases. Therefore, a great deal of discussion has taken place concerning indications for treatment modality, and various procedures have been performed to palliate such patients. The prognosis for such patients is still poor, even though many kinds of palliation have already been developed and applied. To improve the prognosis of such patients we developed a multidisciplinary treatment which includes high dose rate intraluminal brachytherapy (HDR-ILBRT) and evaluated its effectiveness, especially the HDR-ILBRT component. PATIENTS AND TREATMENT METHODS: Sixty-six patients with unresectable esophageal cancer enrolled in this study. Twenty-seven patients underwent bypass operations. Seven of the 27 patients received external irradiation only (group BE), 11 received external irradiation and HDR-ILBRT (group BEH), while the remaining 9 did not receive radiotherapy (group B). Another 39 patients without bypass operations were all treated with radiotherapy, 22 with external irradiation only (group E) and 17 were treated with external irradiation and HDR-ILBRT (group EH). After completion of radiotherapy, all patients received chemotherapy with 5-FU (2,500 mg/body) and CDDP (100 mg/body).

RESULTS

Mean survival time and the 5-year survival rate of group BEH (13.3 +/- 1.5 months and 20%) were significantly improved compared with group BE + B (p < 0.05). In the patients without bypass operations, there were significant differences in the mean survival time and the 3-year survival rate in groups EH and E (group EH 16.5 +/- 2.5 months, 21.8%, group E 9.0 +/- 1.3 months, 0%, p < 0.05). The bypass operation itself and chemotherapy did not significantly affect the prognosis of patients with unresectable esophageal cancer.

CONCLUSION

These results strongly suggest the use of HDR-ILBRT, as a component of multidisciplinary treatment for unresectable esophageal cancer, was significantly effective and HDR-ILBRT contributed to improve outcomes in patients with advanced esophageal cancer. HDR-ILBRT should be established as a component of treatments for unresectable esophageal cancer.

Conservation treatment intensified with an anti-estrogen agent and CAF chemotherapy for stage I and II breast cancer

In order to improve both cosmetic results and survival rates, we performed breast-conservation treatment (BCT) intensified with tamoxifen and CAF chemotherapy to 218 out of 224 patients who visited our department with the desire of breast-conservation between August 1989 to December 1998. Of these patients, 68 presented with tumors of stage I, and another 122 stage II. All patients were administered tamoxifen (for pre-menopausal women) or tremifene (for post-menopausal women) orally: tamoxifen and tremifene administration was started just after confirmation of the breast cancer based on the findings of fine-needle aspiration cytology. All patients underwent lumpectomy with or without axillary dissection (level I and II). For patients with T2 tumors, the lumpectomy was performed following two to four times of CAF chemotherapy. Following conservative surgery, patients were treated with radiation therapy to the intact breast and ipsilateral axilla to a total dose of 4400 cGy with a conedown to a total median dose of 5300 cGy. At the end of March 1999, the mean follow-up time was 49.0 months. In spite of high-positivity (approximately 30%) of microscopically surgical margin, local recurrence rate is considerably low, and only 2 patients experienced local recurrence. Cause-specific survival rate for patients of stage I is 100%, and that of stage II is 91.7% at 5 years. The cosmetic results of therapy were also considered good.