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Chronic Chlamydophila pneumoniae infection in lung cancer, a risk factor: a case–control study

Cerrahpaa Faculty of Medicine, Istanbul University, Department of Microbiology and Clinical Microbiology, Istanbul, Turkey

Correspondence Bekir Kocazeybek bekirkcz{at}superonline.com

Received December 3, 2001
Accepted January 21, 2003

	Abstract

TOP Abstract INTRODUCTION METHODS RESULTS DISCUSSION Acknowledgements REFERENCES

 
The relationship between chronic Chlamydophila (formerly Chlamydia) pneumoniae infection and lung carcinoma was investigated. A total of 123 patients who were smokers and diagnosed with lung carcinoma based on clinical and laboratory (radiological, cytological) findings were examined. Of these patients, 70 had small-cell, 28 squamous-cell and seven large-cell carcinomas, while 18 had adenocarcinoma. A total of 123 healthy persons matching patients in age, sex, duration of smoking and locality were chosen as controls. Blood samples (5 ml) were withdrawn at the time of diagnosis and 1 month later. The values between IgG 512 and IgA 40 were set as the criteria for chronic Chlamydophila pneumoniae infections. In male patients with lung carcinoma, Chlamydophila pneumoniae IgG antibody titres of 512 and IgA antibody titres of 40 were found at a higher rate than in the control group. This ratio was not significant for the female patients. In chronic Chlamydophila pneumoniae infections, Chlamydophila pneumoniae antibody titres with values IgG 512 and IgA 40 were found in a total of 62 (50.4 %) cases. Chronic Chlamydophila pneumoniae infections were seen statistically more often in male patients with carcinoma who were aged 55 years or younger. This study supports the idea that chronic Chlamydophila pneumoniae infection increases the risk of lung carcinoma.

	INTRODUCTION

TOP Abstract INTRODUCTION METHODS RESULTS DISCUSSION Acknowledgements REFERENCES

 
Chlamydophila (formerly Chlamydia) pneumoniae, and previously also known as strain TWAR, is a Gram-negative bacillus and an obligatory intracellular parasite (Grayston, 1989; Everett et al., 1999). It causes infection in more than 50 % of adults. It leads to a higher incidence of pneumonia in the elderly, while children younger than 5 years old have less clinical infection (Saikku, 1992). Chlamydophila pneumoniae infections vary in different countries and populations, being endemic in the USA and epidemic in Scandinavian countries. The route of transmission is usually by aerosol and respiratory secretions (Grayston, 1989; Thom & Grayston, 1991). Since it is difficult to isolate the organism in culture, serological analysis is preferred in diagnosis. However, it could not be established as a routine method due to very few elementary substances in samples (Grayston et al., 1990). PCR, known to be 25 % more sensitive than culture, is often used for diagnosis, but serum antibody determination, especially microimmunofluorescence (MIF), is the most frequently used method for the diagnosis of chlamydia infections (Gaydos et al., 1993; Grayston, 1994). Chlamydophila pneumoniae causes various infections, such as pneumonia, sinusitis, bronchitis, rhinitis, chronic obstructive pulmonary disease (COPD) or asymptomatic infection. The specific antibody titres of Chlamydophila pneumoniae have been found to be high in myocardial infarction, stable angina pectoris and atherosclerosis cases. In addition, detection of Chlamydophila pneumoniae in atherosclerotic plaques on coronary and carotid arteries, led to discussion about the cause–effect relationship between Chlamydophila pneumoniae and atherosclerosis and coronary heart disease (Saikku et al., 1988; Grayston et al., 1993; Arat et al., 1999). In the last 3 years, seroepidemiological studies have indicated a possible relation between Chlamydophila pneumoniae infection and lung carcinoma and malignant lymphoma (Koyi et al., 1999; Laurila et al., 1997a). In this study, we aimed to evaluate the relationship between chronic Chlamydophila pneumoniae infection and lung carcinoma by determining antibodies against Chlamydophila pneumoniae in patients with lung carcinoma who are smokers.

	METHODS

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A total of 123 cases diagnosed as primary lung carcinoma with clinical symptoms and laboratory findings (radiological, cytological) consisting of 70 (56.91 %) small-cell carcinoma, 28 (22.76 %) squamous-cell carcinoma, 18 (14.63 %) adenocarcinoma and seven (5.69 %) large-cell carcinoma cases, were included in this study. The subjects were admitted to the Oncology and Lung Diseases Departments in the Florence Nightingale Group between 1 June 1998 and 1 July 2000. One hundred and one (82.11 %) of the cases were male and 22 (17.88 %) were female, with ages between 22 and 87 and a mean of 55 years (53 males were < 55, 48 were 55 years old; 10 females were < 55 and 12 were 55 years old). The duration of smoking before the diagnosis of primary lung carcinoma was between 3 and 58 years with a mean of 32 years. A control group of 123 people was chosen from among healthy hospital staff, relatives of the patients, blood donors or persons with similar age, sex and smoking habits. In the selection of the control group, the following criteria were taken into consideration: age, sex, living environment, smoking history, including the following: age of starting smoking, whether or not he or she is still a smoker, number of cigarettes per day, duration of smoking, and if smoking stopped, total time of smoking.

Of the control group, 101 (82.11 %) were males and 22 (17.88 %) were females. Their ages were 22–87 years with a mean of 55 years (53 males were < 55, 48 were 55 years old; 10 females were < 55 and 12 were 55 years old) and smoking periods were between 5 and 58 years with a mean of 32 years. The main criteria accepted for the control group consisted of not having any medical treatment for a local or systemic disease and not being admitted to a hospital in the last 2 months (Table 1).

Blood samples (5 ml) were obtained from the patient group with primary lung carcinoma at the time of diagnosis and the second samples were obtained at the end of the following month. Similarly, the first blood samples were obtained from the control group at the time they were selected and the second samples were obtained at the end of the first month. Serological studies were performed with a Chlamydophila pneumoniae MIF kit (Orgenium). In these kits, the elementary bodies of Chlamydophila pneumoniae were used as an antigen on slides. In order to eliminate contradictory results, Chlamydia trachomatis and Chlamydophila psittaci antigens were used as controls. Serum dilutions were started at 1/8 for IgG and at 1/10 for IgA and continued in twofold dilutions. As a conjugate, FITC-labelled goat anti-human IgA and IgG were used and all were evaluated by the same investigator (B. K.) using a fluorescence microscope with 40 x 0.65 oil-immersion objective. Seropositivity criteria for the diagnosis of chronic Chlamydophila pneumoniae infection were IgG 512 and IgA 40 and for the community population titres of IgG 16 were accepted as the criterion for previous infection. In both the patient and the control groups, the highest result among the first or second blood samples was accepted as the final titre (Leinonen et al., 1991; Saikku, 1993; Grayston et al., 1989; Forsey et al., 1986).

The Mc-Namar test was used in univariate analysis because patient and control groups were matched individually. Logistic regression method was used for the multivariate analysis. Forward conditional method was selected for this model.

	RESULTS

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Basic characteristics of the matched lung cancer group and patient group are shown in Table 1. The number of cases having infection with titres 16 was 98 (79.7 %) for the patient group and 54 (43.2 %) for the control group (P < 0.001), as shown in Table 2. There was a significant difference between male patients with lung cancer and their control group for specific Chlamydophila pneumoniae antibody titres of IgG 16, IgG 512 and IgA 40 (P < 0.001). On the other hand, female patients and their control group showed no significant difference. However serological evidence of chronic Chlamydophila pneumoniae infection was found more often in male patients with lung cancer than female patients (Table 3). The comparison of lung carcinoma cases with the control group, on the basis of percentage prevalence of the specific antibody seropositivity of Chlamydophila pneumoniae at titres of IgG 512 and IgA 40 based on age and sex, is shown in Table 4. Titres indicative of chronic Chlamydophila pneumoniae infection were significantly higher in male patients with lung carcinoma below age 55 than the control group [S² 28.66, P < 0.001, odds ratio (OR) 18, CI (95 %) 6.2–51.8]. Conversely, no difference was found between male patients with lung carcinoma over age 55 and the control group (P > 0.05). No significant difference was detected in the serological results between female patients and the female control group below age 55 and over age 55 years (P > 0.05). Variants included in the logistic regression model are shown in the legend to Table 5. According to this they were found to be significant. In the multiple logistic regression model, IgG 16 and IgA 40 were found significant. Results were determined for each variant in order for IgG 16 ß = 1.684, P < 0.0001, OR 5.38, CI (95 %) 2.939–9.866 and for IgA 40 ß = 1.684, P < 0.0001, OR 4.583, CI (95 %) 2.525–8.32. According to this, the risk of the raised antibody titres at IgG 16 and IgA 40 is greater in the patient group than in the control group. The number of the cases having infection with titres of IgG 512 and IgA 40 was 62 (50.4 %) for the patient group; 41 lung carcinomas were of the small-cell type (Table 6).

View this table: [in this window] [in a new window]   Table 6. Distribution of chronic Chlamydophila pneumoniae infection with IgG 512 and IgA 40 according to histological type of lung carcinoma

	DISCUSSION

TOP Abstract INTRODUCTION METHODS RESULTS DISCUSSION Acknowledgements REFERENCES

 
Saikku et al. (1988, 1992) demonstrated the seroepidemiological correlation between coronary heart diseases and atherosclerosis and infection by Chlamydophila pneumoniae, and proposed that chronic chlamydia infection of the upper and lower respiratory tract may initiate acute myocardial infarction and may be the cause of chronic arthritis in atherosclerosis. Grayston et al. (1993) and Kuo et al. (1993) have shown the presence of Chlamydophila pneumoniae in atheromatous plaques. In the following years, the occurrence of Chlamydophila pneumoniae in atherosclerotic plaques in arteries other than the coronaries, such as the carotids, was demonstrated by seroepidemiological, immunohistochemical and molecular biological methods, leading to implication of this bacterium in aetiology and pathogenesis (Yamashita et al., 1998; Maass et al., 1998). Studies concerning the role of Chlamydophila pneumoniae in the pathogenesis of juvenile arthritis and reactive arthritis in distal extremities (Moazed et al., 1996; Kol et al., 1998) and the study of Blasi et al. (1997) on the relationship between sarcoidosis and Chlamydophila pneumoniae showed correlations on the basis of seropositivity; however, Chlamydophila pneumoniae was not detected by nested PCR in tissue samples. Recently, Anttila et al. (1998) have detected Chlamydophila pneumoniae-specific antibodies at high titres in 72 patients with lymphoma. In all studies, the common question was whether Chlamydophila pneumoniae had an effect in initiating the disease or merely shows affinity for pre-formed lesions. Most investigators (Kol et al., 1998; Moazed et al., 1996, 1997) accept the idea that the infection chain in the respiratory tract is initiated by the infection of monocytes. The agent, which proliferates in the monocytes and macrophages, provokes the pathogenesis and is responsible for the clinical symptoms. Clinical symptoms start with the antigenic response, followed by the infection of new monocytes, endothelial cells, and macrophages in the intima and smooth muscle cells in the media layer, so that cytokines and acute-phase proteins become active, producing chronic inflammation. In recent years, some investigators have suggested that Chlamydophila pneumoniae has a different role in the aetiopathogenesis, for example the high Chlamydophila pneumoniae antibody titres detected in lung carcinomas found in smokers (Laurila et al., 1997a, b; Koyi et al., 1999). In this study, chronic Chlamydophila pneumoniae infection seropositivity was found in 50.81 % of the patient group, and small-cell and squamous-cell carcinomas were detected especially in the cases with chronic Chlamydophila pneumoniae infection seropositivity. Laurila et al. (1997b) found evidence that Chlamydophila pneumoniae infection was present especially in patients with small-cell and squamous-cell carcinomas selected among 230 smokers with lung carcinoma. Koyi et al. (1999) reported that in Sweden in 1993, seropositivity ratios were significantly different from the control group in 117 smokers with lung carcinoma. Korvenan et al. (1994) showed the significant correlation of seropositivity of Chlamydophila pneumoniae with smoking. von Hertzen et al. (1998) suggested that smoking destroys lung and bronchial immunity, increases the secretion of IL4, and as a result, humoral immunity increases and cellular immunity is suppressed, so Chlamydophila pneumoniae can localize easily in the lung. Some studies (Ohshima & Bartsch, 1994; Redecke et al., 1998) explain the pathogenesis of Chlamydophila pneumoniae infections as invasion of the lung with the help of smoking: superoxide oxygen radicals, TNF-, IL1ß and IL8, which are produced and secreted by the monocytes activated by the antigen and the macrophages in the intima, then cause damage to lung tissue and DNA that results in carcinogenesis; in particular, IL8 is known to cause genetic damage. Another suggestion is that, by unknown mechanisms, Chlamydophila pneumoniae infection causes irregular apoptosis in tissues (Fan et al., 1998).

In this study, a significant difference was found between male patients who smoked and controls in IgG positivity at titres 16; male smokers had a greater level of contact with Chlamydophila pneumoniae in the past (P < 0.001). In a recent study, it has been stated that in people below age 60 years, specific Chlamydophila pneumoniae IgA positivity at titres of 216 is independently related to carcinoma (Jackson et al., 2000). A group of investigators in Sweden has indicated that male patients particularly had a high level of contact with Chlamydophila pneumoniae (IgG 32 positivity) in the past, and these patients had IgG 512 and IgA 64 values which were significantly higher than the control group: even 48 % of the young male patients were shown to have IgA titres of 512 (Koyi et al., 1999). It has been reported that patients with lung carcinoma have very high titres of IgA. We have found the risk of the elevation of titration of Chlamydophila pneumoniae antibody titres at IgA 40 is greater in the lung cancer group than the control group according to the multivariate regression analysis.

In this study, 54 % of the male patients and 36 % of the female patients were diagnosed as having chronic seropositivity for Chlamydophila pneumoniae, and a significant difference was found in male patients when compared (P < 0.001) with the control group (Table 5). This difference was especially seen in male patients below the age of 55. In a Finnish study, the seropositivity ratios of chronic Chlamydophila pneumoniae was found to be high in 231 male smoking patients below the age of 60. Similar results have been reported with studies dealing with male patients who were smokers below the age of 70 and above the age of 60 (Laurila et al., 1997a; Koyi et al., 1999; Jackson et al., 2000).

However, age and sex are not thought to be factors in the multivariate analysis. As a result, the detection of chronic Chlamydophila pneumoniae infection in young, smoking, male lung carcinoma patients, at high ratios in univariate analysis and the elevation of IgG 16 and IgA 40 titres compared with the control group, suggests that infection together with age, sex and smoking is a high risk factor in lung carcinoma development. It is not possible to conclude from this study whether chronic Chlamydophila pneumoniae infection will increase the risk of lung cancer or whether patients with lung cancer will be at greater risk of picking up Chlamydophila pneumoniae. In order to define the possible association between chronic Chlamydophila pneumoniae infection and lung cancer, further studies with a larger number of cases are necessary.

	Acknowledgements

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I would like to thank Professor Dr Seyhan Çelikolu from the Kadir Has University, Florence Nightingale Hospital, Thoracic Diseases Dept, and Dr A. Suat Sarba from the Cerrahpaa Faculty of Medicine Microbiology and Clinical Microbiology Dept, and also my co-workers, Dr Mesut Gencay and Kadir Salam for their contributions to this study.

	REFERENCES

TOP Abstract INTRODUCTION METHODS RESULTS DISCUSSION Acknowledgements REFERENCES

 

Arat, A., Kocazeybek, B., Enar, R., Orhon, R. & Pehlivanolu, S. (1999). Chlamydia pneumoniae kararl Anjina Pektoris ilikisi. 15. Ulusal Kardiyoloji Kongresi 9–12 Ekim 1999 I2zmir 362.