Sharon R. Pine

Increased Levels of Circulating Interleukin 6, Interleukin 8, C-Reactive Protein, and Risk of Lung Cancer

BACKGROUNDnPrevious studies that were based primarily on small numbers of patients suggested that certain circulating proinflammatory cytokines may be associated with lung cancer; however, large independent studies are lacking.nnnMETHODSnAssociations between serum interleukin 6 (IL-6) and interleukin 8 (IL-8) levels and lung cancer were analyzed among 270 case patients and 296 control subjects participating in the National Cancer Institute-Maryland (NCI-MD) case-control study. Results were validated in 532 case patients and 595 control subjects in a nested case-control study within the prospective Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. Association with C-reactive protein (CRP), a systemic inflammation biomarker, was also analyzed. Associations between biomarkers and lung cancer were estimated using logistic regression models adjusted for smoking, stage, histology, age, and sex. The 10-year standardized absolute risks of lung cancer were estimated using a weighted Cox regression model.nnnRESULTSnSerum IL-6 and IL-8 levels in the highest quartile were associated with lung cancer in the NCI-MD study (IL-6, odds ratio [OR] = 3.29, 95% confidence interval [CI] = 1.88 to 5.77; IL-8, OR = 2.06, 95% CI = 1.19 to 3.57) and with lung cancer risk in the PLCO study (IL-6, OR = 1.48, 95% CI = 1.04 to 2.10; IL-8, OR = 1.57, 95% CI = 1.10 to 2.24), compared with the lowest quartile. In the PLCO study, increased IL-6 levels were only associated with lung cancer diagnosed within 2 years of blood collection, whereas increased IL-8 levels were associated with lung cancer diagnosed more than 2 years after blood collection (OR = 1.57, 95% CI = 1.15 to 2.13). The 10-year standardized absolute risks of lung cancer in the PLCO study were highest among current smokers with high IL-8 and CRP levels (absolute risk = 8.01%, 95% CI = 5.77% to 11.05%).nnnCONCLUSIONSnAlthough increased levels of both serum IL-6 and IL-8 are associated with lung cancer, only IL-8 levels are associated with lung cancer risk several years before diagnosis. Combination of IL-8 and CRP are more robust biomarkers than either marker alone in predicting subsequent lung cancer.

p53 isoforms Δ133p53 and p53β are endogenous regulators of replicative cellular senescence

The finite proliferative potential of normal human cells leads to replicative cellular senescence, which is a critical barrier to tumour progression in vivo. We show that the human p53 isoforms Δ133p53 and p53β function in an endogenous regulatory mechanism for p53-mediated replicative senescence. Induced p53β and diminished Δ133p53 were associated with replicative senescence, but not oncogene-induced senescence, in normal human fibroblasts. The replicatively senescent fibroblasts also expressed increased levels of miR-34a, a p53-induced microRNA, the antisense inhibition of which delayed the onset of replicative senescence. The siRNA (short interfering RNA)-mediated knockdown of endogenous Δ133p53 induced cellular senescence, which was attributed to the regulation of p21WAF1 and other p53 transcriptional target genes. In overexpression experiments, whereas p53β cooperated with full-length p53 to accelerate cellular senescence, Δ133p53 repressed miR-34a expression and extended the cellular replicative lifespan, providing a functional connection of this microRNA to the p53 isoform-mediated regulation of senescence. The senescence-associated signature of p53 isoform expression (that is, elevated p53β and reduced Δ133p53) was observed in vivo in colon adenomas with senescent phenotypes. The increased Δ133p53 and decreased p53β isoform expression found in colon carcinoma may signal an escape from the senescence barrier during the progression from adenoma to carcinoma.

C-Reactive Protein and Risk of Lung Cancer

PURPOSEnChronic inflammation could play a role in lung carcinogenesis, underscoring the potential for lung cancer prevention and screening. We investigated the association of circulating high-sensitivity C-reactive protein (CRP, an inflammation biomarker) and CRP single nucleotide polymorphisms (SNPs) with prospective lung cancer risk.nnnPATIENTS AND METHODSnWe conducted a nested case-control study of 592 lung cancer patients and 670 controls with available prediagnostic serum and 378 patients and 447 controls with DNA within the screening arm of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (N = 77,464). Controls were matched to patients on age, sex, entry year, follow-up time, and smoking. We measured CRP levels in baseline serum samples and genotyped five common CRP SNPs.nnnRESULTSnElevated CRP levels were associated with increased lung cancer risk (odds ratio [OR], 1.98; 95% CI, 1.35 to 2.89; P-trend < .001 for fourth quartile [Q4, > or = 5.6 mg/L] v Q1 [< 1.0 mg/L]). The CRP association did not differ significantly by histology, follow-up time, or smoking status, but was most apparent for squamous cell carcinomas (OR, 2.92; 95% CI, 1.30 to 6.54), 2 to 5 years before lung cancer diagnosis (OR, 2.33; 95% CI, 1.24 to 4.39), and among former smokers (OR, 2.48; 95% CI, 1.53 to 4.03) and current smokers (OR, 1.90; 95% CI, 1.06 to 3.41). Although CRP SNPs and haplotypes were associated with CRP levels, they were not associated with lung cancer risk. Ten-year standardized absolute risks of lung cancer were higher with elevated CRP levels among former smokers (Q4: 2.55%; 95% CI, 1.98% to 3.27% v Q1: 1.39%; 95% CI, 1.07% to 1.81%) and current smokers (Q4: 7.37%; 95% CI, 5.81% to 9.33% v Q1: 4.03%; 95% CI, 3.01% to 5.40%).nnnCONCLUSIONnElevated CRP levels are associated with subsequently increased lung cancer risk, suggesting an etiologic role for chronic pulmonary inflammation in lung carcinogenesis.

MDM2 SNP309 and SNP354 Are Not Associated with Lung Cancer Risk

A single nucleotide polymorphism (SNP) in the MDM2 promoter (a T to G exchange at nucleotide 309) has been found to be associated with tumor formation. Publication of this null report is important because an association between MDM2 SNP309 and lung cancer was previously reported in two independent studies. Our findings suggest that MDM2 SNP309 is not a strong factor in lung carcinogenesis. In addition, this is the first MDM2 SNP309 report on a population consisting of Caucasians in the United States and African-Americans. A strength of the study design is that the controls consist of both population and hospital controls. (Cancer Epidemiol Biomarkers Prev 2006;15(8):1559–61)

p53 isoforms regulate aging- and tumor-associated replicative senescence in T lymphocytes

Cellular senescence contributes to aging and decline in tissue function. p53 isoform switching regulates replicative senescence in cultured fibroblasts and is associated with tumor progression. Here, we found that the endogenous p53 isoforms Δ133p53 and p53β are physiological regulators of proliferation and senescence in human T lymphocytes in vivo. Peripheral blood CD8+ T lymphocytes collected from healthy donors displayed an age-dependent accumulation of senescent cells (CD28-CD57+) with decreased Δ133p53 and increased p53β expression. Human lung tumor-associated CD8+ T lymphocytes also harbored senescent cells. Cultured CD8+ blood T lymphocytes underwent replicative senescence that was associated with loss of CD28 and Δ133p53 protein. In poorly proliferative, Δ133p53-low CD8+CD28- cells, reconstituted expression of either Δ133p53 or CD28 upregulated endogenous expression of each other, which restored cell proliferation, extended replicative lifespan and rescued senescence phenotypes. Conversely, Δ133p53 knockdown or p53β overexpression in CD8+CD28+ cells inhibited cell proliferation and induced senescence. This study establishes a role for Δ133p53 and p53β in regulation of cellular proliferation and senescence in vivo. Furthermore, Δ133p53-induced restoration of cellular replicative potential may lead to a new therapeutic paradigm for treating immunosenescence disorders, including those associated with aging, cancer, autoimmune diseases, and HIV infection.

Childhood Exposure to Secondhand Smoke and Functional Mannose Binding Lectin Polymorphisms Are Associated with Increased Lung Cancer Risk

Background: Exposure to secondhand smoke during adulthood has detrimental health effects, including increased lung cancer risk. Compared with adults, children may be more susceptible to secondhand smoke. This susceptibility may be exacerbated by alterations in inherited genetic variants of innate immunity genes. We hypothesized a positive association between childhood secondhand smoke exposure and lung cancer risk that would be modified by genetic polymorphisms in the mannose binding lectin-2 (MBL2) gene resulting in well-known functional changes in innate immunity. Methods: Childhood secondhand smoke exposure and lung cancer risk was assessed among men and women in the ongoing National Cancer Institute-Maryland Lung Cancer (NCI-MD) study, which included 624 cases and 348 controls. Secondhand smoke history was collected via in-person interviews. DNA was used for genotyping the MBL2 gene. To replicate, we used an independent case-control study from Mayo Clinic consisting of 461 never smokers, made up of 172 cases and 289 controls. All statistical tests were two-sided. Results: In the NCI-MD study, secondhand smoke exposure during childhood was associated with increased lung cancer risk among never smokers [odds ratio (OR), 2.25; 95% confidence interval (95% CI), 1.04-4.90]. This was confirmed in the Mayo study (OR, 1.47; 95% CI, 1.00-2.15). A functional MBL2 haplotype associated with high circulating levels of MBL and increased MBL2 activity was associated with increased lung cancer risk among those exposed to childhood secondhand smoke in both the NCI-MD and Mayo studies (OR, 2.52; 95% CI, 1.13-5.60, and OR, 2.78; 95% CI, 1.18-3.85, respectively). Conclusions: Secondhand smoke exposure during childhood is associated with increased lung cancer risk among never smokers, particularly among those possessing a haplotype corresponding to a known overactive complement pathway of the innate immune system. (Cancer Epidemiol Biomarkers Prev 2009;18(12):3375–83)

Lung Cancer Stem Cells

Lung cancer remains a major cause of cancer-related lethality because of high incidence and recurrence in spite of significant advances in staging and therapies. Recent data indicates that stem cells situated throughout the airways may initiate cancer formation. These putative stem cells maintain protumorigenic characteristics including high proliferative capacity, multipotent differentiation, drug resistance and long lifespan relative to other cells. Stem cell signaling and differentiation pathways are maintained within distinct cancer types, and destabilization of this machinery may participate in maintenance of cancer stem cells. Characterization of lung cancer stem cells is an area of active research and is critical for developing novel therapies. This review summarizes the current knowledge on stem cell signaling pathways and cell markers used to identify the lung cancer stem cells.

Admixture mapping of lung cancer in 1812 African-Americans

Lung cancer continues to be the leading cause of cancer death in the USA and the best example of a cancer with undisputed evidence of environmental risk. However, a genetic contribution to lung cancer has also been demonstrated by studies of familial aggregation, family-based linkage, candidate gene studies and most recently genome-wide association studies (GWAS). The African-American population has been underrepresented in these genetic studies and has patterns of cigarette use and linkage disequilibrium that differ from patterns in other populations. Therefore, studies in African-Americans can provide complementary data to localize lung cancer susceptibility genes and explore smoking dependence-related genes. We used admixture mapping to further characterize genetic risk of lung cancer in a series of 837 African-American lung cancer cases and 975 African-American controls genotyped at 1344 ancestry informative single-nucleotide polymorphisms. Both case-only and case-control analyses were conducted using ADMIXMAP adjusted for age, sex, pack-years of smoking, family history of lung cancer, history of emphysema and study site. In case-only analyses, excess European ancestry was observed over a wide region on chromosome 1 with the largest excess seen at rs6587361 for non-small-cell lung cancer (NSCLC) (Z-score = -4.33; P = 1.5 × 10⁻⁵) and for women with NSCLC (Z-score = -4.82; P = 1.4 × 10⁻⁶). Excess African ancestry was also observed on chromosome 3q with a peak Z-score of 3.33 (P = 0.0009) at rs181696 among ever smokers with NSCLC. These results add to the findings from the GWAS in Caucasian populations and suggest novel regions of interest.

Manganese superoxide dismutase gene coding region polymorphisms lack clinical incidence in general population.

Two functional polymorphisms within the manganese superoxide dismutase (MnSOD) gene have been reported to lead to increased oxidative stress damage. The MnSOD 58T > C single nucleotide polymorphism (SNP) within exon 3 changes isoleucine to threonine, leading to decreased thermal stability and reduced enzymatic activity in vivo and in vitro. The MnSOD 60C > T polymorphism within exon 3 changes leucine to phenylalanine, rendering the protein sensitive to redox regulation by intracellular thiols. Thus, the goal of this study was to evaluate the 58T > C and 60C > T MnSOD polymorphisms in a large case-control study. Taqman allelic discrimination assays were developed to identify the 58T > C and 60C > T SNPs in exon 3. Two hundred and eight lung cancer cases and 141 controls were evaluated for these two SNPs, and all 349 subjects were of the wild-type homozygous genotype for both 58C and 60T in exon 3. This study suggests that although the 58T > C and 60C > T polymorphisms reduce MnSOD enzymatic activity, these polymorphisms were not identified in the present case-control study population.