Protective Effect of Withaferin-A on Micronucleus Frequency and Detoxication Agents During Experimental Oral Carcinogenesis

Our aim was to investigate the effect of Withaferin-A on bone marrow micronucleus frequency and buccal mucosa detoxication agents during 7, 12-dimethylbenz[a]anthracene (DMBA) induced hamster buccal pouch carcinogenesis. Oral squamous cell carcinoma was developed in hamsters'' buccal pouches by painting 0.5% DMBA in liquid paraffin, three times per week for 14 weeks. We observed 100% tumor formation in DMBA painted hamsters. Elevated frequency of bone marrow micronucleated polychromatic erythrocytes (MnPCEs) and decrease in buccal mucosa phase II detoxication agents were noticed in tumor bearing hamsters. Oral administration of Withaferin-A significantly reduced the micronucleus frequency and brought back the status of phase II detoxication agents in DMBA painted hamsters. Our study thus demonstrated the protective effect of Withaferin-A on DMBA-induced micronucleus frequency in the bone marrow of golden Syrian hamsters. Also, Withaferin-A maintained the status of buccal mucosa detoxication agents during DMBA-induced hamster buccal pouch carcinogenesis.     

Antitumor initiating potential of rosmarinic acid in 7,12-dimethylbenz(a)anthracene-induced hamster buccal pouch carcinogenesis

Oral cancer accounts for 40%-50% of all cancers in India. Tobacco and alcohol are the major etiological factors contributing to its pathogenesis. The aim of the present study was to explore the key mechanism behind the inhibitory effects of rosmarinic acid against 7,12-dimethylbenz(a)anthracene (DMBA)-induced oral carcinogenesis by evaluating the status of biochemical markers (lipid peroxidation, antioxidants, and detoxification enzymes) and immunoexpression patterns of p53 and bcl-2 proteins. Oral tumors were developed by painting the buccal pouches of golden Syrian hamsters with 0.5% DMBA in liquid paraffin 3 times a week for 14 weeks. We noticed 100% tumor formation in hamsters treated with DMBA alone, and the tumors were histopathologically confirmed as well-differentiated squamous cell carcinoma. Oral administration of rosmarinic acid (100 mg/kg body wt) to DMBA-treated hamsters completely prevented the tumor formation. In addition, rosmarinic acid significantly returned the status of biochemical and molecular markers to near normal range in DMBA-treated hamsters. The results of the present study suggest that rosmarinic acid suppresses oral carcinogenesis by stimulating the activities of detoxification enzymes, improves the status of lipid peroxidation and antioxidants, and downregulates the expression of p53 and bcl-2 during DMBA-induced oral carcinogenesis.     

Protective Role of Withaferin-A on Red Blood Cell Integrity During 7,12-Dimethylbenz[a]anthracene Induced Oral Carcinogenesis

The aim of the present study was to investigate the protective effect of Withaferin-A on red blood cell integrity during 7,12-dimethylbenz[a]anthracene (DMBA) induced oral carcinogenesis. The protective effect of Withaferin-A was assessed by measuring the status of glycoconjugates, membrane bound enzyme activity and red blood cell osmotic fragility. Oral squamous cell carcinoma was induced in the buccal pouch of Syrian golden hamsters by painting with 0.5% DMBA in liquid paraffin thrice a week for 14 weeks. The levels of glycoconjugates, membrane bound enzyme activity, osmotic fragility and thiobarbituric acid reactive substances (TBARS) were analyzed by using specific colorimetric methods. We observed 100% tumor formation in DMBA painted hamsters. Increase in plasma glycoconjugates at the expense of red blood cell membrane glycoconjugates levels were observed in DMBA painted hamsters as compared to control hamsters. Erythrocytes from DMBA painted hamsters were more fragile than those from control hamsters. The activity of membrane bound enzyme (Na⁺ K⁺ ATPase) decreased whereas TBARS level was increased in DMBA painted hamsters as compared to control hamsters. Oral administration of Withaferin-A at a dose of 20mg kg⁻¹ bw significantly prevented the tumor formation as well as normalized the biochemical variables in DMBA painted hamsters. Our results thus demonstrate the protective effect of Withaferin-A on red blood cell integrity during DMBA induced oral carcinogenesis.     

Clerodendron Inerme Protects Cellular Integrity during 7,12-Dimethylbenz[A]-Anthracene Induced Hamster Buccal Pouch Carcinogenesis

Aim of the present study was to investigate the protective effect of Clerodendron inerme on cellular integrity by measuring the status of glycoconjugates, lipids, osmotic fragility, and membrane bound enzyme activity in 7, 12-dimethylbenz (a) anthracene (DMBA)-induced oral carcinogenesis. Oral squamous cell carcinoma was induced in the buccal pouch of Syrian golden hamsters by painting with 0.5% DMBA in liquid paraffin thrice a week for 14 weeks. The levels of glycoconjugates, lipids, osmotic fragility and membrane bound enzyme activity were analyzed by using specific colorimetric methods. We observed 100% tumor formation in DMBA painted hamsters. Altered glycoconjugates and lipid pattern were observed in DMBA painted hamsters as compared to control hamsters. Erythrocytes from DMBA painted hamsters were more fragile than those from control hamsters. The activity of membrane bound enzyme (Na⁺ K⁺ ATPase) decreased in DMBA painted hamsters as compared to control hamsters. Oral administration of aqueous leaf extract of Clerodendron inerme (CiALet) at a dose of 500mg/kg body weight significantly prevented the tumor formation and histopathological abnormalities as well as normalized the above said biochemical variables in DMBA painted hamsters. Our results thus demonstrate the protective effect of Clerodendron inerme on cellular integrity during DMBA induced oral carcinogenesis.     

穿心莲内酯对口腔癌生长的影响

 目的：探讨穿心莲内酯对口腔癌的作用及其机制。方法：用穿心莲内酯及其对照药物治疗金黄地鼠颊囊癌,通过测量肿瘤体积观察治疗效果。用免疫组化检测穿心莲内酯对肿瘤血管和肿瘤细胞增殖的作用,用TUNEL法检测穿心莲内酯对肿瘤细胞凋亡的作用,用免疫组化检测凋亡信号分子caspase-3的表达情况。结果：穿心莲内酯治疗组颊囊癌的肿瘤体积明显比对照组小,肿瘤微血管密度和增殖的肿瘤细胞也明显低于对照组,肿瘤细胞的凋亡率明显高于对照组,而且治疗组中caspase-3明显被活化。结论:穿心莲内酯通过抑制肿瘤血管生成和肿瘤细胞增殖以及促进肿瘤细胞凋亡,抑制了金黄地鼠颊囊癌的生长。穿心莲内酯通过caspase-3途径诱导了肿瘤细胞的凋亡。     

Effect of granulocyte macrophage-colony stimulating factor (GM-CSF) on 5-FU-induced ulcerative mucositis in hamster buccal pouches.

The present study was performed to investigate the protective effects of granulocyte macrophage-colony stimulating factor (GM-CSF) against ulcerative mucositis in hamster buccal pouch. GM-CSF was topically administered to the buccal pouches of hamsters with two different doses of 5 and 20 microg/ml. The treatment of GM-CSF led to rapid healing effects in gross and histopathological findings. It decreased expression of pro-inflammatory cytokine mRNA levels in the mucosal tissue of buccal pouches. Also GM-CSF-treated animals showed high numbers of Ki-67 positive cells in basal cell layer. These results suggest that GM-CSF provided excellent healing effects to ulcerative mucositis in the buccal pouch of hamster.     

Protective effect of ferulic acid on 7,12-dimethylbenz[a]anthracene-induced skin carcinogenesis in Swiss albino mice

Our aim was to evaluate and compare the chemopreventive potential of topically applied and orally administered ferulic acid in 7,12-dimethylbenz[a]anthracene (DMBA)-induced skin carcinogenesis. Estimating the status of phase I and phase II detoxication agents, lipid peroxidation byproducts and antioxidants during DMBA-induced skin carcinogenesis assessed the mechanistic pathway for its chemopreventive efficacy. Skin squamous cell carcinoma was induced in the shaved back of mice, by painting with DMBA (25 μg in 0.1 mL^?1 acetone) twice weekly for 8 weeks. We have observed 100% tumor formation in the 15th week of experimental period in mice treated with DMBA alone. Marked alterations in the status of phase I and phase II detoxication agents, lipid peroxidaton byproducts and antioxidants were observed in tumor bearing mice. Oral administration of ferulic acid completely prevented the formation of skin tumors, whereas topically applied ferulic acid did not show significant chemopreventive activity during DMBA-induced mouse skin carcinogenesis. Also, oral administration of ferulic acid reverted the status of phase I and phase II detoxication agents, lipid peroxidaton byproducts and antioxidants to near-normal range in DMBA-treated mice. Our results thus demonstrate that orally administered ferulic acid has potent suppressing effect on cell proliferation during DMBA-induced skin carcinogenesis. This is probably due to its modulating effect on the status of lipid peroxidation, antioxidants and detoxication agents during DMBA-induced skin carcinogenesis.     

Protective effect of Picroliv, the active constituent of Picrorhiza kurroa, against chemical carcinogenesis in mice.

Cancer chemoprevention of chemically induced tumours by Picroliv, an iridoid glycoside mixture purified from Picrorhiza kurroa, was studied on 20-methylcholanthrene (20-MC)-induced sarcoma model and 7,12-dimethylbenz[a]anthracene (DMBA)-initiated papilloma formation in BALB/c mice. Administration of Picroliv (100 and 200 mg/kg, p.o) inhibited the sarcoma development by 47 and 53% as estimated on day 200 after 20-MC administration. Control animals started dying of tumour burden 76 days after 20-MC administration and all animals were dead by day 170, while 60 and 66% of the animals survived in the Picroliv treated group, 100 and 200 mg/kg, respectively. Picroliv exhibited anti-tumour-promoting activity on a two-stage carcinogenesis test on mouse skin using DMBA as an initiator and croton oil as a promoter. Topical application of Picroliv (1 and 5 mg/mouse) 30 minutes prior to that of croton oil application resulted in a 50 and 60% reduction in the number of animals that developed papillomas, and 48 and 64% reduction in the number of papillomas per mouse. There was also a delay in the onset of first skin tumour in the group of animals treated with Picroliv. Oral administration of Picroliv (150 mg/kg, p.o.) prior to DMBA application delayed the onset of papillomas and the percent of mice (60%) with tumours indicates that Picroliv inhibited the tumour initiation induced by DMBA. Picroliv administration was also found to increase the life span of transplanted Dalton's Lymphoma Ascites (DLA) and Ehrlich Ascites Carcinoma (EAC) harboring mice and reduced the volume of transplanted solid tumours.     

Genistein and daidzein, in combination, protect cellular integrity during 7,12-dimethylbenz[a]anthracene (DMBA) induced mammary carcinogenesis in Sprague-Dawley rats

The status of glycoconjugates (protein bound hexose, hexosamine, sialic acid and fucose) in plasma or serum serve as potential biomarkers for assessing tumor progression and therapeutic interventions. Aim of the present study was to investigate the protective effect of two major soy isoflavones, genistein and daidzein, in combination on the status of glycoconjugates in plasma, erythrocyte membrane and mammary tissues during 7,12-dimethylbenz[a]anthracene (DMBA) induced mammary carcinogenesis in female Sprague-Dawley rats. A single subcutaneous injection of DMBA (25 mg rat(-1)) in the mammary gland developed mammary carcinoma in female Sprague-Dawley rats. Elevated levels of plasma and mammary tissue glycoconjugates accompanied by reduction in erythrocyte membrane glycoconjugates were observed in rats bearing mammary tumors. Oral administration of genistein + daidzein (20 mg + 20 mg kg(-1) bw/day) to DMBA treated rats significantly (p< 0.05) brought back the status of glycoconjugates to near normal range. The present study thus demonstrated that genistein and daidzein in combination protected the structural integrity of the cell surface and membranes during DMBA-induced mammary carcinogenesis.     

Expression of inhibitors of apoptosis family protein in 7,12-dimethylbenz[a]anthracene-induced hamster buccal-pouch squamous-cell carcinogenesis is associated with mutant p53 accumulation and epigenetic changes

Fifty outbred Syrian golden hamsters were equally divided into three experimental groups and two control groups. The pouches of the experimental groups were painted bilaterally with a 0.5% 7,12-dimethylbenz[a]anthracene (DMBA) solution thrice a week for 3, 7 and 14 weeks. One of the control groups was applied with mineral oil while another control group remained untreated throughout the experiment. Neither survivin nor cIAP2 could be detected in any of the control tissues, whereas survivin and cIAP2 were found to be significantly increased in 3-, 7- and 14-week DMBA-treated pouches compared with the control pouches. Expression of XIAP, cIAP1 and NAIP were noted for both the control and 3-, 7- and 14-week DMBA-treated pouches, but levels were found to be significantly elevated in the experimental groups compared with the control pouches. p53 was not detected in any control tissues, but was significantly increased in 3-, 7- and 14-week DMBA-treated pouches. Direct sequencing revealed a point mutation (C-->G) of p53 for pouch tissues treated with DMBA for 3 and 7 weeks, and there was a wide variation in the p53 sequence of the 14-week DMBA-treated pouch tissues, as compared with the control tissues. The control tissues had a survivin- and cIAP2-methylated allele, whereas the DMBA-treated tissues showed no evidence of survivin- and cIAP2-methylation. Neither the control nor DMBA-treated pouches showed evidence of XIAP-, cIAP1- or NAIP-methylation. Our results suggest that the expression of inhibitors of apoptosis family in DMBA-induced hamster buccal-pouch squamous-cell carcinogenesis may be modulated by both genetic (mutant p53) and epigenetic mechanisms.     

Morphological characterization of cellular and extracellular components of 7,12 dimethylbenz[a]anthracene induced melanoma tumours.

Subcutaneous tumours were induced in castrated golden Syrian hamsters by 7,12 dimethylbenz[a]anthracene (DMBA), an agent known to produce papillomas and carcinomas. The morphological characteristics of the cellular and extracellular constituents of the chemically-induced tumours were indicative of melanoma. Tumours were induced by three injections of DMBA into the jugular vein over a 3 month period. Dermal tumour development within the dorsal integument and groin region ultimately projected into the epidermis and occurred during the 3 month period subsequent to the last DMBA injection. Suspect melanoma tumours were excised and processed for light microscopic (LM) and transmission electron microscopic (TEM) studies. Histochemical staining methods facilitated the characterization of the differentiated tumour components in this hamster melanoma model. The model presented could allow observations from initial melanoma transformation events through advanced stages of metastasis within a window of 7 months.     

Morphological characterization of cellular and extracellular components of 7,12 dimethylbenz[a]anthracene induced melanoma tumours

Subcutaneous tumours were induced in castrated golden Syrian hamsters by 7,12 dimethylbenz[a]anthracene (DMBA), an agent known to produce papillomas and carcinomas. The morphological characteristics of the cellular and extracellular constituents of the chemically-induced tumours were indicative of melanoma. Tumours were induced by three injections of DMBA into the jugular vein over a 3 month period. Dermal tumour development within the dorsal integument and groin region ultimately projected into the epidermis and occurred during the 3 month period subsequent to the last DMBA injection. Suspect melanoma tumours were excised and processed for light microscopic (LM) and transmission electron microscopic (TEM) studies. Histochemical staining methods facilitated the characterization of the differentiated tumour components in this hamster melanoma model. The model presented could allow observations from initial melanoma transformation events through advanced stages of metastasis within a window of 7 months.     

The biochemical and morphological alterations following administration of melatonin, retinoic acid and Nigella sativa in mammary carcinoma: an animal model

Worldwide, breast cancer is the second leading cause of cancer death among women and the third most common cancer. Although our understanding of the molecular basis of this fatal disease has improved, this malignancy remains elusive. Melatonin (Mel), retinoic acid (RA) and Nigella sativa (NS) are substances with anticancer effects. To date, our understanding of the mechanisms of therapeutic effects of these products in mammary cancer is still marginal. To look at the preventive and therapeutic values of these products, we carried out this investigation. An animal model formed of 80 rats was established. The animals were divided into eight groups of 10 animals each: (a) control group injected with the same vehicle used for treatments in the relevant dosages and routes; (b) carcinogen group injected with the known carcinogenic substance 7,12-di-methylbenz(a)anthracene (DMBA) that induces mammary carcinoma; (c) three prophylactic (Pro) groups (Mel-Pro, RA-Pro and NS-Pro) injected with test substances (Mel, RA and NS, respectively) 14 days before the intake of the carcinogenic substance DMBA and then continued until the end of the experiments; and (d) three treated (Tr) groups (Mel-Tr, RA-Tr and NS-Tr) injected with the vehicles after the intake of DMBA. In both the Pro and Tr groups, the drugs were daily administered for 3 months. The animals were killed, and their serum and tissues were evaluated for (a) markers of tumorigenicity [serum levels of total sialic acid (TSA) and lipid-bound sialic acid (LSA)], (b) markers of endocrine derangement (serum prolactin, estradiol and progesterone levels), (c) apoptotic changes [serum tumour necrosis factor (TNF)-alpha, tissue caspase-3 activity, percentage of DNA fragmentation and ultrastructural features of apoptosis] and (d) markers of oxidative stress (tissue levels of lipid peroxides and nitric oxide). Carcinoma was absent both in the control and in the NS-Pro groups. Mammary carcinoma occurred in DMBA and other Pro and Tr groups. The frequency of mammary carcinoma was high in the carcinogen DMBA group (60%), followed by the Tr (56%) and finally the Pro groups (33%). These tumours included papillary, comedo and cribriform carcinomas. As compared with the control group, the development of carcinoma in the carcinogen DMBA group was associated with increased levels of (a) markers of tumorigenicity (77.0 +/- 3.3 vs. 209.0 +/- 5.6 and P < 0.05 for TSA; 28.7 +/- 1.7 vs. 41.8 +/- 1.2 and P < 0.01 for LSA), (b) markers of endocrine derangement (2.5 +/- 0.1 vs. 3.6 +/- 0.3 and P < 0.05 for prolactin; 39.6 +/- 1.3 vs. 24.8 +/- 2.1 and P < 0.01 for progesterone and 31.0 +/- 0.7 vs. 51.1 +/- 3.4 and P < 0.01 for estradiol) and (c) markers of oxidative stress (2.3 +/- 0.2 vs. 5.2 +/- 0.7 and P < 0.01 for lipid peroxides and 4.4 +/- 0.2 vs. 7.6 +/- 0.8 and P < 0.01 for nitric oxide). Also, it was associated with decreased levels of markers of apoptotic activity (20.8 +/- 1.1 vs. 13.4 +/- 0.7 and P < 0.01 for caspase-3; 29.0 +/- 1.7 vs. 20.9 +/- 1.3 and P < 0.05 for percentage of DNA fragmentation; and 9.4 +/- 0.8 vs. 52.1 +/- 3.3 and P < 0.01 for TNF-alpha). When compared with the carcinogen DMBA group, the development of carcinoma in the Pro and Tr groups was associated with decreased levels of (a) markers of tumorigenicity, (b) markers of endocrine derangement and (c) markers of oxidative stress. Alternatively, carcinogenicity was associated with statistically significant (P < 0.01) increased levels of markers of apoptotic activity. To conclude, the administration of Mel, RA and NS reduced the carcinogenic effects of DMBA, suggesting a protective role. The possible underlying mechanisms of these effects await further investigations.     

Antigenotoxic Effect of Ferulic Acid in 7,12-Dimethyl Benz(a)-Anthracene (DMBA) Induced Genotoxicity

The antigenotoxic effect of ferulic acid was carried out by evaluating the cytogenetic markers, the micronuclei frequency and chromosomal aberrations, in the bone marrow of hamsters in 7,12-dimethylbenz(a)anthracene (DMBA) induced genotoxicity. Genotoxicity was induced in experimental hamsters by single intraperitoneal injection of DMBA (30mg kg⁻¹ b.w). Pretreatment of ferulic acid orally at a dose of 40mg kg⁻¹ b.w for five days significantly reduced the frequency of micronucleated polychromatic erythrocytes (MnPCEs) and the percentage of chromosomal aberrations in hamster''s bone marrow. Our results thus suggest that ferulic acid has potent antigenotoxic effect in DMBA induced genotoxicity in golden Syrian hamsters.     

Modifying effects of antioxidants on chemical carcinogenesis

Studies were made on the carcinogenic activity of butylated hydroxyanisole (BHA) in rats, mice, and hamsters and the effect of the antioxidants BHA, butylated hydroxytoluene (BHT), ethoxyquin (EQ), sodium L-ascorbate (SA), ascorbic acid (AA), sodium erythorbate (SE), propyl gallate (PG), and alpha-tocopherol, on two-stage chemical carcinogenesis in rats initiated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), 1,2-dimethylhydrazine (DMH), diethylnitrosamine (DEN), 7,12-dimethylbenz(a)anthracene (DMBA), N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN), N-ethyl-N-hydroxyethylnitrosamine (EHEN), or N-methylnitrosourea (MNU). BHA clearly induced squamous cell carcinomas in both the rat and hamster forestomach. The tumorigenic action of crude BHA on the forestomach is largely due to 3-tert-BHA. In two-stage chemical carcinogenesis, BHA promoted MNNG or MNU-initiated forestomach and BBN- or MNU-initiated urinary bladder carcinogenesis and inhibited DEN- or EHEN-initiated liver and DMBA-initiated mammary carcinogenesis. BHT demonstrated promotion potential for urinary bladder and MNU-initiated thyroid carcinogenesis and inhibited DMBA-initiated ear duct carcinogenesis. EQ promoted EHEN-initiated kidney carcinogenesis and inhibited DMBA-initiated mammary and EHEN-initiated liver carcinogenesis. SA promoted forestomach and urinary bladder carcinogenesis and SE likewise enhanced urinary bladder carcinogenesis. alpha-Tocopherol inhibited ear duct carcinogenesis. No effects of any of the antioxidants on glandular stomach carcinogenesis were found. The results clearly demonstrated that antioxidants have different effects (promoting or inhibitory influences) depending on the organ studied and suggest the importance of a whole body approach to their investigation.     

In vivo multiphoton fluorescence lifetime imaging of protein-bound and free nicotinamide adenine dinucleotide in normal and precancerous epithelia

Multiphoton fluorescence lifetime imaging microscopy (FLIM) is a noninvasive, cellular resolution, 3-D functional imaging technique. We investigate the potential for in vivo precancer diagnosis with metabolic imaging via multiphoton FLIM of the endogenous metabolic cofactor nicotinamide adenine dinucleotide (NADH). The dimethylbenz[alpha]anthracene (DMBA)-treated hamster cheek pouch model of oral carcinogenesis and MCF10A cell monolayers are imaged using multiphoton FLIM at 780-nm excitation. The cytoplasm of normal hamster cheek pouch epithelial cells has short (0.29+/-0.03 ns) and long lifetime components (2.03+/-0.06 ns), attributed to free and protein-bound NADH, respectively. Low-grade precancers (mild to moderate dysplasia) and high-grade precancers (severe dysplasia and carcinoma in situ) are discriminated from normal tissues by their decreased protein-bound NADH lifetime (p<0.05). Inhibition of cellular glycolysis and oxidative phosphorylation in cell monolayers produces an increase and decrease, respectively, in the protein-bound NADH lifetime (p<0.05). Results indicate that the decrease in protein-bound NADH lifetime with dysplasia is due to a shift from oxidative phosphorylation to glycolysis, consistent with the predictions of neoplastic metabolism. We demonstrate that multiphoton FLIM is a powerful tool for the noninvasive characterization and detection of epithelial precancers in vivo.     

SV40 lymphomagenesis in Syrian golden hamsters

Simian virus 40 (SV40) isolates differ in oncogenic potential in Syrian golden hamsters following intraperitoneal inoculation. Here we describe the effect of intravenous exposure on tumor induction by SV40. Strains SVCPC (simple regulatory region) and VA45-54(2E) (complex regulatory region) were highly oncogenic following intravenous inoculation, producing a spectrum of tumor types. Three lymphoma cell lines were established; all expressed SV40 T-antigen, were immortalized for growth in culture, and were tumorigenic following transplantation in vivo. New monoclonal antibodies directed against hamster lymphocyte surface antigens are described. The cell lines expressed MHC class II and macrophage markers and were highly phagocytic, indicating a histiocytic origin. Many hamsters that remained tumor-free developed SV40 T-antigen antibodies, suggesting that viral replication occurred. This study shows that route of exposure influences the pathogenesis of SV40-mediated carcinogenesis, that SV40 strain VA45-54(2E) is lymphomagenic in hamsters, that hamster lymphoid cells of histiocytic origin can be transformed in vivo and established in culture, and that reagents to hamster leukocyte differentiation molecules are now available.     

Malignancy of proliferative pulmonary lesions in the Syrian hamster following inhalation of 239PuO2.

The malignancy of pulmonary lesions induced by inhaled 239PuO2 in the Syrian hamster was tested by transplantation in the hamster cheek pouch. Serving as negative and positive controls, 42 female hamsters were given either 0.9% sodium chloride (NaCl), ferric oxide suspended in NaCl (Fe2O3), or benzo(a)pyrene + Fe2O3 suspended in NaCl (BP), by intratracheal instillation. One hundred female hamsters were given a single, nose-only inhalation exposure to high-fired 239PuO2 (initial lung burden, 2.4 kBq). At intervals from 160 to 425 days after Pu inhalation or instillation, ten 1-mm3 tissue cubes were removed from the lung of each hamster and transplanted into the cheek pouch of male hamsters, for a total of 1320 transplantations. None of the lung transplants from hamsters receiving 239PuO2, NaCl, or Fe2O3 grew in recipient cheek pouches, but 14% of transplants from BP hamsters grew rapidly in the cheek pouch. Lung carcinomas were histologically identified only in BP hamsters and BP transplants. It was concluded that proliferative pulmonary lesions induced by a-irradiation of the lung of hamsters were not malignant, and that the malignancy of lung lesions in the hamster induced by ionizing radiation should be evaluated by transplantation.