Chlamydia pneumoniae infection and risk for lung cancer.
BACKGROUND
We evaluated the relationship of Chlamydia pneumoniae infection with prospective lung cancer risk using traditional serologic markers [microimmunoflourescence (MIF) IgG and IgA antibodies] and Chlamydia heat shock protein-60 (CHSP-60) antibodies, a marker for chronic chlamydial infection.


METHODS
We conducted a nested case-control study (593 lung cancers and 671 controls) within the screening arm of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (N = 77,464). Controls were matched to cases by age, sex, randomization year, follow-up time, and smoking (pack-years of smoking, time since quitting). We assessed C. pneumoniae seropositivity and endpoint antibody titers (IgG and IgA against C. pneumoniae elementary bodies and IgG against CHSP-60).


RESULTS
C. pneumoniae seropositivity by microimmunoflourescence IgG or IgA antibodies was not associated with lung cancer [odds ratio of 0.88 and 95% confidence interval (95% CI) of 0.69-1.13 for IgG; odds ratio of 0.98 and 95% CI of 0.75-1.27 for IgA]. In contrast, individuals seropositive for CHSP-60 IgG antibodies had significantly increased lung cancer risk (odds ratio, 1.30; 95% CI, 1.02-1.67), and risk increased with increasing antibody titers (P trend = 0.006). CHSP-60-related risk did not differ significantly by lung cancer histology, follow-up time, or smoking. CHSP-60 seropositivity was associated with increased risk 2 to 5 years before lung cancer diagnosis (odds ratio, 1.77; 95% CI, 1.16-2.71; P trend = 0.006), thus arguing against reverse causality.


CONCLUSIONS
CHSP-60 seropositivity and elevated antibody titers were associated with significantly increased risk for subsequent lung cancer, supporting an etiologic role for C. pneumoniae infection in lung carcinogenesis.


CONCLUSIONS
Our results highlight the potential for lung cancer risk reduction through treatments targeted toward C. pneumoniae infections and chronic pulmonary inflammation.
Chaturvedi
Anil K
AK
Infections and Immunoepidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, Rockville, MD 20852, USA. chaturva@mail.nih.gov
Gaydos
Charlotte A
CA
Agreda
Patricia
P
Holden
Jeffrey P
JP
Chatterjee
Nilanjan
N
Goedert
James J
JJ
Caporaso
Neil E
NE
Engels
Eric A
EA
D000368:Aged; D000906:Antibodies / Q000097:blood; D016022:Case-Control Studies; D018834:Chaperonin 60 / Q000276:immunology; D023521:Chlamydophila Infections / Q000097:blood / Q000150:complications*; D016993:Chlamydophila pneumoniae / Q000302:isolation & purification*; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D008175:Lung Neoplasms / Q000097:blood / Q000382:microbiology*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors
D000906:Antibodies; D018834:Chaperonin 60; D007070:Immunoglobulin A; D007074:Immunoglobulin G