Association of longer telomere length in cancer cells and cancer-associated fibroblasts with worse prognosis.

BACKGROUND: Telomere dysfunction has been reported to be directly involved in carcinogenesis owing to chromosomal instability and immortalization; however, the clinicopathological significance of telomeres remains controversial. We have shown that telomere shortening occurs in normal-appearing duct cells at initiation and then continues during the progression of pancreatic cancer. In this study, we determined the clinicopathological and prognostic value of telomere length (TL) in cancer progression. METHODS: TL in both cancer cells and cancer-associated fibroblasts (CAFs) was analyzed by high-throughput quantitative fluorescence in situ hybridization using a previously reported cohort comprising 1434 cases of adenocarcinoma (ADC), squamous cell carcinoma (SCC), adenosquamous carcinoma, hepatocellular carcinoma, and renal cell carcinoma (RCC), which are known cancers with a statistically significantly low incidence of alternative lengthening of telomeres. Cases were divided into 2 groups as follows: longer and shorter telomeres, according to the median TL of cancer cells and CAFs. The statistical significance of TL in cancer cells and CAFs on clinicopathological characteristics and prognosis was analyzed. RESULTS: There was a close association between TL in cancer cells and CAFs. Longer telomeres in cancer cells and CAFs were associated with aggressive features such as advanced stage, high mitosis score and nuclear score, poorly differentiated cancer, and desmoplastic stroma in ADC. Furthermore, a longer TL was an independent prognostic factor for ADC, SCC, and RCC. CONCLUSIONS: Longer telomeres are associated with worse prognosis in ADC, SCC, and RCC. Thus, TL is a novel biomarker for the diagnosis of aggressive cancers with poor prognoses.

An International Collaborative Animal Study of the Carcinogenicity of Mobile Phone Radiofrequency Radiation: Considerations for Preparation of a Global Project.

Radiofrequency radiation (RFR) was classified as a "possible" human carcinogen in 2011, which caused great public concern. A carcinogenicity study by the National Toxicology Program (NTP) found Code Division Multiple Access-and Global System for Mobile Communications-modulated mobile phone RFR to be carcinogenic to the brain and heart of male rats. As part of an investigation of mobile phone carcinogenesis, and to verify the NTP study results, a 5-year collaborative animal project was started in Korea and Japan in 2019. An international animal study of this type has two prerequisites: use of the same study protocol and the same RF-exposure system. This article discusses our experience in the design of this global study on radiofrequency electromagnetic fields (RF-EMFs).© 2022 The Authors. Bioelectromagnetics published by Wiley Periodicals LLC on behalf of Bioelectromagnetics Society.

Relationship between Lung Carcinogenesis and Chronic Inflammation in Rodents.

Lung cancer remains the leading cause of cancer-related deaths, with an estimated 1.76 million deaths reported in 2018. Numerous studies have focused on the prevention and treatment of lung cancer using rodent models. Various chemicals, including tobacco-derived agents induce lung cancer and pre-cancerous lesions in rodents. In recent years, transgenic engineered rodents, in particular, those generated with a focus on the well-known gene mutations in human lung cancer (KRAS, EGFR, and p53 mutations) have been widely studied. Animal studies have revealed that chronic inflammation significantly enhances lung carcinogenesis, and inhibition of inflammation suppresses cancer progression. Moreover, the reduction in tumor size by suppression of inflammation in animal experiments suggests that chronic inflammation influences the promotion of tumorigenesis. Here, we review rodent lung tumor models induced by various chemical carcinogens, including tobacco-related carcinogens, and transgenics, and discuss the roles of chronic inflammation in lung carcinogenesis.

Single Intratracheal Quartz Instillation Induced Chronic Inflammation and Tumourigenesis in Rat Lungs.

Crystalline silica (quartz) is known to induce silicosis and cancer in the lungs. In the present study, we investigated the relationship between quartz-induced chronic inflammation and lung carcinogenesis in rat lungs after a single exposure to quartz. F344 rats were treated with a single intratracheal instillation (i.t.) of quartz (4 mg/rat), and control rats were treated with a single i.t. of saline. After 52 or 96 weeks, the animals were sacrificed, and the lungs and other organs were used for analyses. Quartz particles were observed in the lungs of all quartz-treated rats. According to our scoring system, the lungs of rats treated with quartz had higher scores for infiltration of lymphocytes, macrophages and neutrophils, oedema, fibrosis, and granuloma than the lungs of control rats. After 96 weeks, the quartz-treated rats had higher incidences of adenoma (85.7%) and adenocarcinoma (81.0%) than control rats (20% and 20%, respectively). Quartz-treated and control rats did not show lung neoplastic lesions at 52 weeks after treatment. The number of lung neoplastic lesions per rat positively correlated with the degree of macrophage and lymphocyte infiltration, oedema, fibrosis, and lymph follicle formation around the bronchioles. In conclusion, single i.t. of quartz may induce lung cancer in rat along with chronic inflammation.

Lung proliferative lesion-promoting effects of left pulmonary ligation in A/J female mice.

This present study was conducted in an attempt to examine proliferative lesion-promoting effect in the lung by compensatory lung growth after left pulmonary ligation. To examine a strong proliferative lesion-promoting effect in the lung, the effects of left pulmonary ligation on lung proliferative lesions induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) were examined for 12 weeks. The number of proliferative lesions induced by NNK in the right lung after left pulmonary ligation increased significantly after 12 weeks, indicated by an increase in the weight of the right lung. In addition, several messenger RNA (mRNA) markers, including insulin growth factor 1, were highly expressed in the right lung on the seventh day after left ligation. These experiments demonstrated the clear proliferative lesion-promoting effects of pulmonary ligation on the induction of the expression of mRNAs related to the cell cycle, cell division and mitosis. However, the proliferative lesion-promoting effects were not strong enough to allow a shortened experimental period for the establishment of the lung bioassay model. The results also indicated the necessity to pay attention to the possibility of a recurrence of lung cancer in the residual lung after resection in humans.

Characteristics of surfactant proteins in tumorigenic and inflammatory lung lesions in rodents.

Surfactant proteins (SPs) are essential for the proper structure and respiratory function of the lungs. There are four subtypes of SPs: SP-A, SP-B, SP-C, and SP-D. The expectorant drug ambroxol hydrochloride is clinically used to stimulate pulmonary surfactant and airway serous secretion. In addition, previous studies showed that ambroxol regulated SP production and attenuated pulmonary inflammation, with ambroxol hydrochloride being found to suppress quartz-induced lung inflammation via stimulation of pulmonary surfactant and airway serous secretion. In this study, we investigated the expression of SP-A, SP-B, SP-C, and SP-D in neoplastic and inflammatory lung lesions in rodents, as well as their possible application as potential markers for diagnostic purposes. SP-B and SP-C showed strong expression in lung hyperplasia and adenoma, whereas SP-A and SP-D were expressed in the mucus or exudates of inflammatory alveoli. Rodent tumorigenic hyperplasic tissues induced by various carcinogens were positive for napsin A, an aspartic proteinase involved in the maturation of SP-B; this indicated a focal increase in type II pneumocytes in the lungs. Therefore, high expression of napsin A in the alveolar walls may serve as a useful marker for prediction of the tumorigenic potential of lung hyperplasia in rodents.

Effects of the expectorant drug ambroxol hydrochloride on chemically induced lung inflammatory and neoplastic lesions in rodents.

Ambroxol hydrochloride (AH) is an expectorant drug used to stimulate pulmonary surfactant and serous airway secretion. Surfactant proteins (SPs) are essential for maintaining respiratory structure and function, although SP expression has also been reported in lung inflammatory and proliferative lesions. To determine whether AH exerts modulatory effects on these lung lesions, we examined its effects on pleural thickening induced by intrathoracic administration of dipotassium titanate (TISMO) in A/JJmsSlc (A/J) mice. We also analyzed the modulatory effects of AH on neoplastic lung lesions induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in A/J mice and by N-nitrosobis (2-hydroxypropyl) amine (DHPN) in F344/DuCrlCrj (F344) rats. A/J mice treated with TISMO showed decreased body weight, increased white blood cell (WBC) counts, and pleural thickening caused by pleuritis and poor general condition. However, A/J mice treated with TISMO + 120 ppm showed significant recovery of body weight and WBC counts to the same levels as those of A/J mice not treated with TISMO, although no significant differences were observed in histopathological changes including the immunohistopathological expression of IL-1ß in the lung and maximum pleural thickness regardless of AH treatment. In the NNK and DHPN experiments, no significant differences in body weight, hematology, plasma biochemistry, and histopathological changes were associated with AH concentration. These results suggest that AH potentially exerts anti-inflammatory effects but does not have a direct suppressive effect on lung tumorigenesis in rodents.

γH2AX is immunohistochemically detectable until 7 days after exposure of N-bis (2-hydroxypropyl) nitrosamine (DHPN) in rat lung carcinogenesis.

It is known that γH2AX, which is formed when there is a double-strand break in DNA, can act as a sensitive marker of genomic instability. In this experiment, the time-course manner of the expression of γH2AX in the lung was examined in the early phase after treatment with a lung carcinogen, N-bis (2-hydroxypropyl) nitrosamine (DHPN). The expression of γH2AX is expected to be one of the useful markers for lung carcinogenesis in early stages. Rats were separated into 10 groups of 5 rats. The DHPN groups were administered 0.1% DHPN in drinking tap water for two weeks, while the control group received drinking tap water. At 0, 1, 3, 7, and 14 days after finishing DHPN treatment, one group each from the DHPN and control groups was sacrificed. The removed lung tissues were examined for immunostaining of γH2AX and PCNA, and positive cells were counted. The γH2AX levels of the DHPN-treated groups were found to be increased significantly at 0, 1, 3, and 7 days (4.4 ± 1.4, 5.1 ± 2.7, 3.3 ± 1.0, and 4.1 ± 1.3%, respectively), and they dropped significantly on day 14 (1.1 ± 0.4%). The experiment showed that the γH2AX-positive score could be effectively measured for up to 7 days after exposure, as a significance difference was observed between the treated group and the control group. It can be deduced that γH2AX is an effective marker for DHPN-induced double-strand breaks in pulmonary epithelial cells.

Hepatocyte growth factor produced in lung fibroblasts enhances non-small cell lung cancer cell survival and tumor progression.

BACKGROUND: The influence of lung fibroblasts on lung cancer progression is not fully understood. METHODS: Lung fibroblasts (HFL1, MRC5, and IMR90 cells) and non-small cell lung cancer (NSCLC)-derived cell lines (A549, EBC1, and HI1017) were cultured under serum-free conditions, and the resulting culture media were designated "cell-conditioned media". Cell survival (viability) was assessed by WST-1 assay. Concentrations of hepatocyte growth factor (HGF) were measured by ELISA. The BALB/c-nu mouse strain was used for the xenograft model. RESULTS: Lung fibroblast-conditioned media enhanced the survival of the three NSCLC cell lines tested. HGF was produced to a greater extent by lung fibroblasts than NSCLC cells. Exogenous HGF enhanced the survival of NSCLC cells. Either an anti-HGF neutralizing antibody or the Met inhibitor PHA-665752 inhibited the fibroblast-conditioned media-enhanced survival of NSCLC cells. The co-inoculation of mice with NSCLC cells and fibroblasts enhanced tumorigenicity and tumor progression in a mouse xenograft model. PHA-665752 significantly inhibited tumor progression that occurred after the co-inoculation of NSCLC cells and fibroblasts. In addition, HGF production by fibroblasts was stimulated by NSCLC cells. CONCLUSIONS: The current study provides evidence for an interaction between fibroblasts and NSCLC cells via the HGF/Met signaling pathway, which affects NSCLC cell survival and tumor progression. These findings may contribute to the development of anti-cancer-associated fibroblast therapeutic strategies. TRIAL REGISTRATION: No trial registration is required because this study is not a clinical trial. This study does not include any participants or patients.

Validating the use of napsin A as a marker for identifying tumorigenic potential of lung bronchiolo-alveolar hyperplasia in rodents.

There are two types of bronchiolo-alveolar hyperplasia (hyperplasia) in rodent lungs. The first is "inflammatory hyperplasia" that retains its ability to revert to normal epithelia upon removal of the stimulating insult. The second is "latent tumorigenic hyperplasia", which is irreversible and causes independent preneoplastic lesions that can progress to bronchiolo-alveolar adenocarcinoma. Previously, lung samples with hyperplastic lesions were obtained from rats exposed to N-bis (2-hydroxypropyl) nitrosamine (DHPN) and fine particles (e.g. quartz), and 19 specific markers were examined immunohistochemically to identify latent tumorigenic hyperplasia. In the cytoplasm of the cells that make up the alveolar wall, we found that napsin A was weakly expressed in the inflammatory hyperplastic lesions, and was strongly expressed in the latent tumorigenic hyperplastic lesions induced by DHPN. To validate the possibility that napsin A may serve as a tumorigenic hyperplastic marker, additional experiments were performed with rats and mice. Latent tumorigenic hyperplasia induced by various carcinogens were positive for napsin A, similar to hyperplasia induced by DHPN. Thus, high expression of napsin A in alveolar walls may serve as a useful marker for detecting the tumorigenic potential of lung hyperplasia in rodents.

Altered susceptibility of an obese rat model to 13-week subchronic toxicity induced by 3-monochloropropane-1,2-diol.

3-Monochloropropane-1,2-diol (3-MCPD) is a heat-induced food contaminant that has been shown to be a nongenotoxic renal carcinogen. Although the toxicity of 3-MCPD has been widely investigated for decades, there is a further concern that 3-MCPD might exert more potent toxicity in high-risk population with underlying diseases such as hyperlipidemia associated with obesity. In the present study, we performed a 13-week subchronic toxicity study for 3-MCPD using an obesity rat model to investigate the differences in susceptibility between obese and normal individuals. Male F344 and obese Zucker (lean and fatty) rats were administered 0, 9, 28.5, 90, 285, or 900 ppm 3-MCPD in drinking water for 13 weeks. 3-MCPD treatment decreased body weight gain, increased relative kidney weights, induced anemia, and induced epithelial cell necrosis in epididymal ducts in all 3 strains. The degrees of epididymal damage were higher in F344 and lean rats than in fatty rats, while renal toxicity was most potent in F344 rats and comparable in lean and fatty rats. In contrast, the hematology data indicated that anemia was worse in fatty rats than in F344 and lean rats, and a significant decrease in hematopoietic cells in the bone marrow was observed only in fatty rats. The no-observed-adverse-effect level was estimated to be 28.5 ppm in all 3 strains for 3-MCPD. These results suggested that obese Zucker rats may be more susceptible to 3-MCPD-dependent toxicity in the hematopoietic tissues than their lean counterparts.

Chronic mesothelial reaction and toxicity of potassium octatitanate fibers in the pleural cavity in mice and F344 rats.

Fiber-shaped particles of potassium octatitanate (tradename TISMO; chemical formula K2 O·6TiO2 ), which are morphologically similar to asbestos particles, were shown to induce severe proliferative reactions in the pleural mesothelium in a previous experiment carried out over 21 weeks. The present study aims to determine whether these fibers induce malignant mesotheliomas in rodents, and to examine chronic toxicity induced. Additionally, we investigated the specific differences observable between the biological responses to the direct infusion of the fibers alone into the pleural cavity and those induced by the co-administration of the fibers with a known carcinogen. To detect the induction of malignant pleural mesotheliomas, two experiments were undertaken. In Experiment 1, four strains of mice, A/J, C3H, ICR, and C57BL, were examined for 52 weeks after experimental treatment with TISMO. In Experiment 2, the F344 rats were treated with TISMO alone, the lung carcinogen N-bis (2-hydroxypropyl) nitrosamine (DHPN) alone, both TISMO and DHPN, or left untreated and were then examined for 52 weeks. In this experiment, malignant lesion induction was expected in the co-administration group. TISMO fibers were observed in the alveoli, indicating penetration through the visceral pleura in mice and rats. The histopathological detection of TISMO fibers in the liver and kidneys of mice and rats indicated migration of the fibers out of the pleural cavity. Atypical mesothelial cells with severe pleural proliferation were observed, but malignant mesotheliomas were not detected. Among the rats, there were no observed malignant alterations in the mesothelium induced by DHPN-TISMO co-administration.

Activation of MEK1/2-ERK1/2 signaling during NNK-induced lung carcinogenesis in female A/J mice.

The extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway is activated by several growth factors and mitogens, and upregulation has been noted in many human cancers, including examples in the lung. In this study, to study the association of ERK1/2 activation with mutation of Kras encoding an upstream activator of ERK1/2 in lung premalignant lesions, we immunohistochemically examined expression of phosphorylated forms of ERK1/2 (pERK1/2) and MAP/ERK kinase 1/2 (pMEK1/2) proteins and correlation between ERK activation and mutation of Kras encoding an upstream activator of ERK1/2, in a mouse lung carcinogenesis model. Female 7-week-old A/J mice were administered a single dose of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), then maintained without additional treatment until sacrifice at week 52. Histopathologically, adenocarcinomas, adenomas and hyperplasias were observed in the lung. pMEK1/2 was expressed mostly in the cell cytoplasm in all three. In contrast, pERK1/2-positive cells were also relatively rare in any histological types as compared with level of pMEK1/2 expression. However, pERK1/2-positive cells in adenocarcinoma were still markedly more common than in hyperplasias and adenomas (~5-fold, ~4-fold; P < 0.01). Activating mutations of Kras gene at codons 12, 13 and 61 were detected in the majority of adenomas and adenocarcinomas, but without any significant relation to pERK1/2 expression. These results suggest that activation of ERK1/2 plays a key role in malignant transformation during lung carcinogenesis featuring Kras mutaion. Activation of ERK1/2 in lung premalignant lesions was little regardless of the mutation of Kras, and ERK1/2 activation in NNK-induced mouse lung carcinogenesis may be regulated not only by Kras mutation but also other signaling pathway or regulatory factor.

An Autopsy Case of Rapidly Progressing Spindle Cell Carcinoma of the Lung Accompanied with Intratumor Hemorrhage.

BACKGROUND: Spindle cell carcinoma (SPCC) of the lung is a subset of sarcomatoid carcinoma. Its clinical features are unclear because of its rarity. Here, we report an autopsy case of SPCC and review CT findings and chemotherapeutic regimens based on previous reports of this disease. To our knowledge, this is the first reported case of pemetrexed used to treat SPCC. CASE REPORT: A 74-year-old Japanese male presented with dyspnea and contrast-enhanced computed tomography (CT) showed abundant left pleural effusion and a mass in lower lobe of the left lung. By the tumor biopsy, he was diagnosed for SPCC of the lung, cT3N0M1a, stage IV. The tumor was resistant to chemotherapy with carboplatin and pemetrexed, and rapidly progressed. Autopsy revealed abundant hemorrhage within the tumor, which apparently reflects a low-density area in CT. CONCLUSIONS: Present case and the accumulation of cases indicate that low-density areas in CT and rapid tumor progression may be common SPCC findings.

Long-Term Chronic Toxicity and Mesothelial Cell Reactions Induced by Potassium Octatitanate Fibers (TISMO) in the Left Thoracic Cavity in A/J Female Mice.

The present study was conducted to examine the chronic effects of potassium octatitanate fibers (trade name TISMO; chemical formula K2O·6TiO2) on the mouse lung and thoracic cavity. This method of infusion was employed to examine the direct effects of the fibers to the pleura. In the present study, 52- and 65-week experiments were employed to examine the long-term chronic effects after infusion of fiber-shaped TISMO into the thoracic cavities of A/J mice. Following this infusion, TISMO fibers were observed in the alveoli, indicating penetration through the visceral pleura. The additional histopathological detection of TISMO fibers in the liver, spleen, kidneys, ovary, heart, bone marrow, and brain of TISMO-infused mice indicated migration of the fibers out from the thoracic cavity. Atypical mesothelial cells with severe pleural proliferation were observed, but malignant mesotheliomas were not detected. This study demonstrated that intrathoracic infusion of TISMO fiber did not cause malignant mesothelioma but did cause severe chronic inflammation and proliferation of pleural mesothelial cells.

Immunohistochemical characteristics of surfactant proteins a, B, C and d in inflammatory and tumorigenic lung lesions of f344 rats.

Surfactant proteins (SPs), originally known as human lung surfactants, are essential to respiratory structure and function. There are 4 subtypes, SP-A, SP-B, SP-C and SP-D, with SP-A and SP-D having immunological functions, and SP-B and SP-C having physicochemical properties that reduce the surface tension at biological interfaces. In this experiment, the expressions of SP-A, SP-B, SP-C and SP-D in lung neoplastic lesions induced by N-bis (2-hydroxypropyl) nitrosamine (DHPN) and inflammatory lesions due to quartz instillation were examined and compared immunohistochemically. Formalin fixed paraffin embedded (FFPE) lung samples featuring inflammation were obtained with a rat quartz instillation model, and neoplastic lesions, hyperplasias and adenomas, were obtained with the rat DHPN-induced lung carcinogenesis model. In the rat quartz instillation model, male 10-week old F344 rats were exposed by intratracheal instillation (IT) to quartz at a dose of 2 mg/rat suspended in saline (0.2 ml) on day 0, and sacrificed on day 28. Lung tumorigenesis in F344 male rats was initiated by DHPN in drinking water for 2 weeks, and the animals were then sacrificed in week 30. Lung proliferative lesions, hyperplasias and adenomas, were observed with DHPN, and inflammation was observed with quartz. The expressions of SP-A, SP-B, SP-C and SP-D were examined immunohistochemically. SP-B and SP-C showed strong expression in lung hyperplasias and adenomas, while SP-A and SP-D were observed in mucus or exudates in inflammatory alveoli. These results suggest the possibility that SP-B and SP-C are related to lung tumorigenesis.

Significance of the progesterone receptor and epidermal growth factor receptor, but not the estrogen receptor, in chemically induced lung carcinogenesis in female A/J mice.

In the present study, the expression levels of female hormone receptors, estrogen receptor (ER) and progesterone receptor (PR) and the epidermal growth factor receptor, (EGFR), as well as proliferating cell nuclear antigen (PCNA) were examined in lung tumors that were induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in female A/J mice. Each seven-week-old mouse was administered with 2 mg NNK via intraperitoneal injection and the mice were subsequently euthanized at week 52. Lung tumors, including adenomas, carcinomas in adenomas and adenocarcinomas, were obtained and analyzed by immunohistochemistry for the expression levels of the receptors, ER, PR and EGFR, and PCNA. The results were as follows: i) In mouse lung adenomas, a significant correlation was identified between the size of the tumor and PCNA expression, although not with the expression of the receptors (ER, PR and EGFR); ii) in the carcinoma components of the carcinomas in adenomas, the size of the tumor and PCNA expression were correlated, while EGFR expression demonstrated a significant correlation with PR expression; iii) in adenocarcinomas, the tumor size significantly correlated with PCNA, EGFR and PR expression; and iv) EGFR and PR expression was identified to be significantly correlated in adenocarcinomas, and to a certain extent in the carcinoma components of the carcinomas in adenomas, although not in the adenomas. Notably, ER expression was not associated with tumor growth or the other factors, particularly EGFR expression, and no significant differences were identified between the three types of lesion. These results indicate that PR, like EGFR, may be significant in lung carcinogenesis.

[A case of advanced gastric cancer with multiple liver metastases treated with preoperative TS-1/CDDP chemotherapy and resection, with a complete response and survival for 7 years].

CASE: An 82-year-old man died because of squamous cell carcinoma of the right lung with metastasis to the left femoral bone. At the age of 75 years, he was admitted to our hospital because of hematemesis. Widespread type 3 gastric cancer was detected in the lesser curvature. Computed tomography(CT)showed multiple liver metastases. Preoperative chemotherapy with TS-1/cisplatin(CDDP)was administered. TS-1 was orally administered at 80mg/body/day and CDDP was administered by intravenous infusion at 20mg/body/day every week for 3 weeks and this was followed by a drug-free 2-week period as the first course. After the fourth course, gastrectomy was performed for the primary lesion and radiofrequency ablation(RFA)was performed for the liver metastases. The patient survived for more than 7 years with a complete response (CR)and died thereafter because of squamous cell carcinoma of the lung.

Rat strain differences in levels and effects of chronic inflammation due to intratracheal instillation of quartz on lung tumorigenesis induced by DHPN.

Chronic inflammatory effects of single intratracheal instillation (i.t.) of quartz on rat lung tumorigenesis were examined using 4 different animal models. At first, in order to determine an appropriate dose of quartz i.t. to promote lung tumorigenesis, F344 male rats were administrated single 0, 0.5, 1, 2 or 4 mg quartz/rat after initiation by N-bis(2-hydroxypropyl) nitrosamine (DHPN). Further studies were performed to examine strain differences of the effects of chronic inflammation caused by quartz i.t. in 3 strains of rat, i.e. F344, Wistar-Hannover and SD. Each was instilled with 2mg quartz/rat after DHPN administration and sacrificed in week 24. In addition, strain differences in generation of inflammation were determined at days 1 and 28. Finally, for determination of long-term effects period, F344 and Wistar-Hannover rats were similarly treated, but the experiment was terminated at week 52. In F344 rats, the tumor areas in DHPN treated groups showed a tendency to increase along with the dose of quartz. F344 rats demonstrated the highest and Wistar-Hannover rats the lowest sensitivity to quartz in acute and chronic phases in the 3 strains. In 52 week, in F344 rats, the multiplicity of tumors and the serum concentration of IL-6 in the group treated with DHPN and quartz were significantly increased. The present experiments indicated that chronic inflammation due to quartz instillation exerted promoting effects on lung carcinogenesis in F344, SD and Wistar-Hannover rats. The strain differences in tumor promotion appeared to correlate with inflammatory reactions to quartz and increase of IL-6.