Biomarker development in the precision medicine era: lung cancer as a case study

Precision medicine relies on validated biomarkers with which to better classify patients by their probable disease risk, prognosis and/or response to treatment. Although affordable 'omics'-based technology has enabled faster identification of putative biomarkers, the validation of biomarkers is still stymied by low statistical power and poor reproducibility of results. This Review summarizes the successes and challenges of using different types of molecule as biomarkers, using lung cancer as a key illustrative example. Efforts at the national level of several countries to tie molecular measurement of samples to patient data via electronic medical records are the future of precision medicine research.

Genome-wide association study confirms lung cancer susceptibility loci on chromosomes 5p15 and 15q25 in an African-American population

OBJECTIVES

Genome-wide association studies (GWAS) of lung cancer have identified regions of common genetic variation with lung cancer risk in Europeans who smoke and never-smoking Asian women. This study aimed to conduct a GWAS in African Americans, who have higher rates of lung cancer despite smoking fewer cigarettes per day when compared with Caucasians. This population provides a different genetic architecture based on underlying African ancestry allowing the identification of new regions and exploration of known regions for finer mapping.

MATERIALS AND METHODS

We genotyped 1,024,001 SNPs in 1737 cases and 3602 controls in stage 1, followed by a replication phase of 20 SNPs (p<1.51×10(-5)) in an independent set of 866 cases and 796 controls in stage 2.

RESULTS AND CONCLUSION

In the combined analysis, we confirmed two loci to be associated with lung cancer that achieved the threshold of genome-wide significance: 15q25.1 marked by rs2036527 (p=1.3×10(-9); OR=1.32; 95% CI=1.20-1.44) near CHRNA5, and 5p15.33 marked by rs2853677 (p=2.8×10(-9); OR=1.28; 95% CI=1.18-1.39) near TERT. The association with rs2853677 is driven by the adenocarcinoma subtype of lung cancer (p=1.3×10(-8); OR=1.37; 95% CI=1.23-1.54). No SNPs reached genome-wide significance for either of the main effect models examining smoking - cigarettes per day and current or former smoker. Our study was powered to identify strong risk loci for lung cancer in African Americans; we confirmed results previously reported in African Americans and other populations for two loci near plausible candidate genes, CHRNA5 and TERT, on 15q25.1 and 5p15.33 respectively, are associated with lung cancer. Additional work is required to map and understand the biological underpinnings of the strong association of these loci with lung cancer risk in African Americans.

Abstract 127: The genomic landscapes of inflammatory bowel disease-associated colorectal cancers

Long duration inflammatory bowel disease (IBD) increases the risk for colorectal cancer (CRC). Mutation analysis of limited numbers of genes has suggested that CRCs arising in an IBD background differ from those that do not. We sought to characterize the genetic landscape of these tumors through whole-exome sequencing.

Thirty-one IBD patients with CRC were identified, including 15 with ulcerative colitis, 14 with Crohn's disease and 2 with indeterminate colitis. Whole-exome sequencing was performed on micro-dissected tumor and matched non-neoplastic formalin-fixed paraffin-embedded (FFPE) tissues. Somatic alterations were identified by comparing matched specimens. Mutation prevalence in sporadic CRC was obtained from previously published exome-sequencing studies.

An average of 11.6 Gb were sequenced per sample. The depth of quality coverage of the targeted region was 29 to 100-fold in the tumors; and 17- to 123-fold in non-tumor samples. Two specimens harbored somatic mutations in the DNA proofreading or mismatch repair genes POLE, MLH1 and MSH6 and exhibited hypermutable phenotype. The remaining cases had a median mutation rate of 1.33 mutations/Mb and an average of 71 alterations per sample. The pattern of base changes in non-hypermutated tumors showed a preponderance of C to T transitions (62%), a majority of which (48% of all mutations) occurred at 5′-CpG-3′ sites. An excess of A to C transversions at AA dinucleotides, particularly in a context of AAG trinucleotides, was also noted. This pattern has been previously observed in esophageal and gastric cancers, both of which are also tied to chronic inflammation. There were no apparent differences in the spectrum of substitutions between tumors arising in UC and CD patients. We identified 28 genes recurrently mutated in three or more non-hypermutated samples. TP53 was the most commonly mutated gene, with incidence prevalence similar to sporadic CRC (63% of cases), but with different mutation spectrum. APC and KRAS were mutated at significantly lower rates than in sporadic CRCs (13% and 20% of cases, respectively). Genes mutated more commonly or uniquely in IBD-CRC, included SOX9 and EP300, encoding proteins in the WNT pathway, NRG1, encoding an ERBB ligand, and IL16, encoding a cytokine. Three cases featured hotspot PIK3CA mutations. Likely oncogenic driver gene mutations in BRAF, CTNNB1, and CREBBP were found in one case each. Mutated genes were enriched for gene ontologies associated with cell communication, cell-cell signaling, and cell adhesion. Our study also revealed recurrent mutations in components of the Rho/Rac GTPase network, suggesting a role for non-canonical WNT signaling in IBD-CRC.

CRCs arising in IBD patients demonstrate a unique molecular profile, which provides clues to their etiology. Our study also sets the stage for improved early detection of IBD-associated CRCs based on their unique genetic compositions as well as for the tailoring of therapies in this patient population.

Citation Format: Ana I. Robles, Giovanni Traverso, Ming Zhang, Nicholas Roberts, Mohammed A. Khan, Christine Joseph, Gregory Lauwers, Florin Selaru, Maria Popoli, Xiquan Ke, Ralph H. Hruban, Stephen J. Meltzer, Kenneth W. Kinzler, Bert Vogelstein, Curtis C. Harris, Nickolas Papadopoulos. The genomic landscapes of inflammatory bowel disease-associated colorectal cancers. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 127.

Abstract 906: Exosomes from mutant TP53 cancer cells polarize tumor associated macrophages

Introduction: TP53 mutants are involved in the pathogenesis of most solid tumors and are known to gain oncogenic functions distinct from their original wild-type form. The existence of such gain-of-function (GOF) activities is supported by ample evidence, however only in a cell-autonomous fashion. Since tumor-associated-macrophages (TAM) are also a hallmark of solid tumors typically correlated with poor prognosis, we investigated the link between mutations in the TP53 gene (mutp53) occurring in epithelial tumor cells and the formation of a surrounding TAM population in-situ.

Methods: By designing a co-culture system we incubated human primary monocytes together with colorectal cancer (CRC) cells differing in their p53 status. Relevant macrophages markers were evaluated on RNA level and protein level. In addition, co-cultured macrophages were subjected to various functional assays (phagocytosis, migration, and invasion). In attempt to confirm clinical relevance, samples from a cohort of human CRC patients were analyzed using genomic and immunohistochemical methods. To identify the interaction between the tumor cells and the macrophages, we isolated exosomes from the CRC cells and subjected them to a Nanostring analysis to learn about their microRNAs composition.

Results: In this study, we discovered that mutp53 exerts a non-cell-autonomous effect over neighboring macrophages by using specific microRNAs (miRs) which are shuttled through an exosomal transfer resulting with a phenotype change of the affected macrophages. Mutp53-specific exosomes containing cargoes such as miR-1246 were shown to be used by macrophages at the receiving end, thus promoting the formation of TAM subset also observed in surgical specimens resected from cancer patients.

Conclusions: Altogether, these findings are consistent with a microenvironmental role for specific “hot-spot” p53 mutants tightening the interaction between the tumor cell and the immune compartment. Additionally, this study is the first to show a non-cell-autonomous role played by mutant p53 - the most common form of mutation found in human cancers. Deciphering the intricate regulation shared by the tumor cell and its surrounding macrophages may give rise to novel prognostic and diagnostic tools as well as to therapeutic approaches targeting TAM, specific tumor-promoting miRs and mutp53-specific subsets of exosomes.

Citation Format: Tomer Cooks, Ioannis S. Pateras, Keval M. Patel, Tim Forshew, Vassilis G. Gorgoulis, Curtis C. Harris. Exosomes from mutant TP53 cancer cells polarize tumor associated macrophages. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 906.

Female chromosome X mosaicism is age-related and preferentially affects the inactivated X chromosome

To investigate large structural clonal mosaicism of chromosome X, we analysed the SNP microarray intensity data of 38,303 women from cancer genome-wide association studies (20,878 cases and 17,425 controls) and detected 124 mosaic X events >2 Mb in 97 (0.25%) women. Here we show rates for X-chromosome mosaicism are four times higher than mean autosomal rates; X mosaic events more often include the entire chromosome and participants with X events more likely harbour autosomal mosaic events. X mosaicism frequency increases with age (0.11% in 50-year olds; 0.45% in 75-year olds), as reported for Y and autosomes. Methylation array analyses of 33 women with X mosaicism indicate events preferentially involve the inactive X chromosome. Our results provide further evidence that the sex chromosomes undergo mosaic events more frequently than autosomes, which could have implications for understanding the underlying mechanisms of mosaic events and their possible contribution to risk for chronic diseases.

Whole-Exome Sequencing Analyses of Inflammatory Bowel Disease-Associated Colorectal Cancers

BACKGROUND & AIMS

A long duration of inflammatory bowel disease (IBD) increases the risk for colorectal cancer. Mutation analysis of limited numbers of genes has indicated that colorectal tumors that develop in patients with IBD differ from those of patients without IBD. We performed whole-exome sequencing analyses to characterize the genetic landscape of these tumors.

METHODS

We collected colorectal tumor and non-neoplastic tissues from 31 patients with IBD and colorectal cancer (15 with ulcerative colitis, 14 with Crohn's disease, and 2 with indeterminate colitis) and performed whole-exome sequencing analyses of the microdissected tumor and matched nontumor tissues. We identified somatic alterations by comparing matched specimens. The prevalence of mutations in sporadic colorectal tumors was obtained from previously published exome-sequencing studies.

RESULTS

Two specimens had somatic mutations in the DNA proofreading or mismatch repair genes POLE, MLH1, and MSH6 and the tumor cells had a hypermutable phenotype. The remaining tumors had, on average, 71 alterations per sample. TP53 was the most commonly mutated gene, with prevalence similar to that of sporadic colorectal tumors (63% of cases). However, tumors from the patients with IBD had a different mutation spectrum. APC and KRAS were mutated at significantly lower rates in tumors from patients with IBD than in sporadic colorectal tumors (13% and 20% of cases, respectively). Several genes were mutated more frequently or uniquely in tumors from patients with IBD, including SOX9 and EP300 (which encode proteins in the WNT pathway), NRG1 (which encodes an ERBB ligand), and IL16 (which encodes a cytokine). Our study also revealed recurrent mutations in components of the Rho and Rac GTPase network, indicating a role for noncanonical WNT signaling in development of colorectal tumors in patients with IBD.

CONCLUSIONS

Colorectal tumors that develop in patients with IBD have distinct genetic features from sporadic colorectal tumors. These findings could be used to develop disease-specific markers for diagnosis and treatment of patients with IBD and colorectal cancer.

Fusobacterium nucleatum and T Cells in Colorectal Carcinoma

IMPORTANCE

Evidence indicates a complex link between gut microbiome, immunity, and intestinal tumorigenesis. To target the microbiota and immunity for colorectal cancer prevention and therapy, a better understanding of the relationship between microorganisms and immune cells in the tumor microenvironment is needed. Experimental evidence suggests that Fusobacterium nucleatum may promote colonic neoplasia development by downregulating antitumor T cell-mediated adaptive immunity.

OBJECTIVE

To test the hypothesis that a greater amount of F nucleatum in colorectal carcinoma tissue is associated with a lower density of T cells in tumor tissue.

DESIGN, SETTING, AND PARTICIPANTS

A cross-sectional analysis was conducted on 598 rectal and colon carcinoma cases in 2 US nationwide prospective cohort studies with follow-up through 2006, the Nurses' Health Study (participants enrolled in 1976) and the Health Professionals Follow-up Study (participants enrolled in 1986). Tissue collection and processing were performed from 2002 through 2008, and immunity assessment, 2008 through 2009. From 2013 through 2014, the amount of F nucleatum in colorectal carcinoma tissue was measured by quantitative polymerase chain reaction assay; we equally dichotomized positive cases (high vs low). Multivariable ordinal logistic regression analysis was conducted in 2014 to assess associations of the amount of F nucleatum with densities (quartiles) of T cells in tumor tissue, controlling for clinical and tumor molecular features, including microsatellite instability, CpG island methylator phenotype, long interspersed nucleotide element-1 (LINE-1) methylation, and KRAS, BRAF, and PIK3CA mutation status. We adjusted the 2-sided α level to .013 for multiple hypothesis testing.

MAIN OUTCOMES AND MEASURES

Densities of CD3+, CD8+, CD45RO (protein tyrosine phosphatase receptor type C [PTPRC])+, and FOXP3+ T cells in tumor tissue, determined by means of tissue microarray immunohistochemical analysis and computer-assisted image analysis.

RESULTS

F nucleatum was detected in colorectal carcinoma tissue in 76 (13%) of 598 cases. Compared with F nucleatum-negative cases, F nucleatum-high cases were inversely associated with the density of CD3+ T cells (for a unit increase in quartile categories of CD3+ T cells as an outcome: multivariable odds ratio, 0.47 [95% CI, 0.26-0.87]; P for trend = .006). The amount of F nucleatum was not significantly associated with the density of CD8+, CD45RO+, or FOXP3+ T cells (P fortrend = .24, .88, and .014, respectively).

CONCLUSIONS AND RELEVANCE

The amount of tissue F nucleatum is inversely associated with CD3+ T-cell density in colorectal carcinoma tissue. On validation, our human population data may provide an impetus for further investigations on potential interactive roles of Fusobacterium and host immunity in colon carcinogenesis.

Fusobacterium nucleatum and T Cells in Colorectal Carcinoma

IMPORTANCE

Evidence indicates a complex link between gut microbiome, immunity, and intestinal tumorigenesis. To target the microbiota and immunity for colorectal cancer prevention and therapy, a better understanding of the relationship between microorganisms and immune cells in the tumor microenvironment is needed. Experimental evidence suggests that Fusobacterium nucleatum may promote colonic neoplasia development by downregulating antitumor T cell-mediated adaptive immunity.

OBJECTIVE

To test the hypothesis that a greater amount of F nucleatum in colorectal carcinoma tissue is associated with a lower density of T cells in tumor tissue.

DESIGN, SETTING, AND PARTICIPANTS

A cross-sectional analysis was conducted on 598 rectal and colon carcinoma cases in 2 US nationwide prospective cohort studies with follow-up through 2006, the Nurses' Health Study (participants enrolled in 1976) and the Health Professionals Follow-up Study (participants enrolled in 1986). Tissue collection and processing were performed from 2002 through 2008, and immunity assessment, 2008 through 2009. From 2013 through 2014, the amount of F nucleatum in colorectal carcinoma tissue was measured by quantitative polymerase chain reaction assay; we equally dichotomized positive cases (high vs low). Multivariable ordinal logistic regression analysis was conducted in 2014 to assess associations of the amount of F nucleatum with densities (quartiles) of T cells in tumor tissue, controlling for clinical and tumor molecular features, including microsatellite instability, CpG island methylator phenotype, long interspersed nucleotide element-1 (LINE-1) methylation, and KRAS, BRAF, and PIK3CA mutation status. We adjusted the 2-sided α level to .013 for multiple hypothesis testing.

MAIN OUTCOMES AND MEASURES

Densities of CD3+, CD8+, CD45RO (protein tyrosine phosphatase receptor type C [PTPRC])+, and FOXP3+ T cells in tumor tissue, determined by means of tissue microarray immunohistochemical analysis and computer-assisted image analysis.

RESULTS

F nucleatum was detected in colorectal carcinoma tissue in 76 (13%) of 598 cases. Compared with F nucleatum-negative cases, F nucleatum-high cases were inversely associated with the density of CD3+ T cells (for a unit increase in quartile categories of CD3+ T cells as an outcome: multivariable odds ratio, 0.47 [95% CI, 0.26-0.87]; P for trend = .006). The amount of F nucleatum was not significantly associated with the density of CD8+, CD45RO+, or FOXP3+ T cells (P fortrend = .24, .88, and .014, respectively).

CONCLUSIONS AND RELEVANCE

The amount of tissue F nucleatum is inversely associated with CD3+ T-cell density in colorectal carcinoma tissue. On validation, our human population data may provide an impetus for further investigations on potential interactive roles of Fusobacterium and host immunity in colon carcinogenesis.

Urinary Metabolite Risk Biomarkers of Lung Cancer: A Prospective Cohort Study

BACKGROUND

Lung cancer is a major health burden causing 160,000 and 1.6 million deaths annually in the United States and worldwide, respectively.

METHODS

While seeking to identify stable and reproducible biomarkers in noninvasively collected biofluids, we assessed whether previously identified metabolite urinary lung cancer biomarkers, creatine riboside (CR), N-acetylneuraminic acid (NANA), cortisol sulfate, and indeterminate metabolite 561+, were elevated in the urines of subjects prior to lung cancer diagnosis in a well-characterized prospective Southern Community Cohort Study (SCCS). Urine was examined from 178 patients and 351 nondiseased controls, confirming that one of four metabolites was associated with lung cancer risk in the overall case-control set, whereas two metabolites were associated with lung cancer risk in European-Americans.

RESULTS

OR of lung cancer associated with elevated CR levels, and adjusted for smoking and other potential confounders, was 2.0 [95% confidence interval (CI), 1.2-3.4; P= 0.01]. In European-Americans, both CR and NANA were significantly associated with lung cancer risk (OR = 5.3; 95% CI, 1.6-17.6; P= 0.006 and OR=3.5; 95% CI, 1.5-8.4; P= 0.004, respectively). However, race itself did not significantly modify the associations. ROC analysis showed that adding CR and NANA to a model containing previously established lung cancer risk factors led to a significantly improved classifier (P= 0.01). Increasing urinary levels of CR and NANA displayed a positive association with increasing tumor size, strengthening a previously established link to altered tumor metabolism.

CONCLUSION AND IMPACT

These replicated results provide evidence that identified urinary metabolite biomarkers have a potential utility as noninvasive, clinical screening tools for early diagnosis of lung cancer. Cancer Epidemiol Biomarkers Prev; 25(6); 978-86. ©2016 AACR.

The Werner syndrome RECQ helicase targets G4 DNA in human cells to modulate transcription

The Werner syndrome (WS) is a prototypic adult Mendelian progeroid syndrome in which signs of premature aging are associated with genomic instability and an elevated risk of cancer. The WRN RECQ helicase protein binds and unwinds G-quadruplex (G4) DNA substrates in vitro, and we identified significant enrichment in G4 sequence motifs at the transcription start site and 5' ends of first introns (false discovery rate < 0.001) of genes down-regulated in WS patient fibroblasts. This finding provides strong evidence that WRN binds G4 DNA structures at many chromosomal sites to modulate gene expression. WRN appears to bind a distinct subpopulation of G4 motifs in human cells, when compared with the related Bloom syndrome RECQ helicase protein. Functional annotation of the genes and miRNAs altered in WS provided new insight into WS disease pathogenesis. WS patient fibroblasts displayed altered expression of multiple, mechanistically distinct, senescence-associated gene expression programs, with altered expression of disease-associated miRNAs, and dysregulation of canonical pathways that regulate cell signaling, genome stability and tumorigenesis. WS fibroblasts also displayed a highly statistically significant and distinct gene expression signature, with coordinate overexpression of nearly all of the cytoplasmic tRNA synthetases and associated ARS-interacting multifunctional protein genes. The 'non-canonical' functions of many of these upregulated tRNA charging proteins may together promote WS disease pathogenesis. Our results identify the human WRN RECQ protein as a G4 helicase that modulates gene expression in G4-dependent fashion at many chromosomal sites and provide several new and unexpected mechanistic insights into WS disease pathogenesis.

Differential Serum Cytokine Levels and Risk of Lung Cancer Between African and European Americans

BACKGROUND

African Americans have a higher risk of developing lung cancer than European Americans. Previous studies suggested that certain circulating cytokines were associated with lung cancer. We hypothesized that variations in serum cytokine levels exist between African Americans and European Americans, and increased circulating cytokine levels contribute to lung cancer differently in the two races.

METHODS

Differences in 10 serum cytokine levels, IL1β, IL4, IL5, IL6, IL8, IL10, IL12, granulocyte macrophage colony-stimulating factor, IFNγ, and TNFα, between 170 African-American and 296 European-American controls from the National Cancer Institute-Maryland (NCI-MD) case-control study were assessed. Associations of the serum cytokine levels with lung cancer were analyzed. Statistically significant results were replicated in the prospective Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial and the Wayne State University Karmanos Cancer Institute case-control study.

RESULTS

Six cytokines, IL4, IL5, IL8, IL10, IFNγ, and TNFα, were significantly higher among European-American as compared with African-American controls. Elevated IL6 and IL8 levels were associated with lung cancer among both races in all three studies. Elevated IL1β, IL10, and TNFα levels were associated with lung cancer only among African Americans. The association between elevated TNFα levels and lung cancer among European Americans was significant after adjustment for additional factors.

CONCLUSIONS

Serum cytokine levels vary by race and might contribute to lung cancer differently between African Americans and European Americans.

IMPACT

Future work examining risk prediction models of lung cancer can measure circulating cytokines to accurately characterize risk within racial groups.

Prediagnosis Plasma Adiponectin in Relation to Colorectal Cancer Risk According to KRAS Mutation Status

BACKGROUND

Low levels of adiponectin (ADIPOQ; HGNC ID; HGNC:13633), an adipokine, are associated with obesity, adiposity, excess energy balance, and increased risk of colorectal neoplasia. Given the reported association of increased body mass index (BMI) and low-level physical activity with KRAS-mutated colorectal tumor, we hypothesized that low-level plasma adiponectin might be associated with increased risk of KRAS-mutant colorectal carcinoma but not with risk of KRAS wild-type carcinoma.

METHODS

We conducted molecular pathological epidemiology research using a nested case-control study design (307 incident rectal and colon cancer case patients and 593 matched control individuals) within prospective cohort studies, the Nurses' Health Study (152 case patients and 297 control individuals, with blood collection in 1989-1990) and the Health Professionals Follow-up Study (155 case patients and 296 control individuals, with blood collection in 1993-1995). Multivariable conditional logistic regression models and two-sided likelihood ratio tests were used to assess etiologic heterogeneity of the associations.

RESULTS

The association of low-level plasma adiponectin with colorectal cancer risk statistically significantly differed by KRAS mutation status (P heterogeneity = .004). Low levels of plasma adiponectin were associated with KRAS-mutant colorectal cancer (for the lowest vs highest tertile: multivariable odds ratio [OR] = 2.83, 95% confidence interval [CI] = 1.50 to 5.34, P trend = .002) but not with KRAS wild-type cancer (for the lowest vs highest tertile: multivariable OR = 0.83, 95% CI = 0.49 to 1.43, P trend = .48). In secondary analyses, the association between plasma adiponectin and colorectal cancer did not appreciably differ by BRAF or PIK3CA oncogene mutation status.

CONCLUSIONS

Low-level plasma adiponectin is associated with KRAS-mutant colorectal cancer risk but not with KRAS wild-type cancer risk.

Cigarette smoke mediates epigenetic repression of miR-217 during esophageal adenocarcinogenesis

Although microRNAs (miRs) have been implicated in the pathogenesis of various human malignancies, limited information is available regarding mechanisms by which these noncoding RNAs contribute to initiation and progression of tobacco-induced esophageal cancers. In this study, array and quantitative reverse transcriptase-PCR techniques were used to examine miR expression in immortalized esophageal epithelia (IEE) and esophageal adenocarcinoma (EAC) cells cultured in normal media with or without cigarette smoke condensate (CSC). Under relevant exposure conditions, CSC significantly decreased miR-217 expression in these cells. Endogenous levels of miR-217 expression in cultured EAC cells (EACC)/primary EACs were significantly lower than those observed in IEE/ paired normal esophageal tissues. RNA crosslink immunoprecipitation, quantitative reverse transcriptase-PCR (qRT-PCR) and immunoblot experiments demonstrated direct interaction of miR-217 with kallikrein 7 (KLK7), encoding a putative oncogene not previously implicated in EAC. Repression of miR-217 correlated with increased levels of KLK7 in primary EACs, particularly those from smokers. Chromatin and methylated DNA immunoprecipitation experiments demonstrated that CSC-mediated repression of miR-217 coincided with DNMT3b-dependent hypermethylation and decreased occupancy of nuclear factor 1 within the miR-217 genomic locus. Deoxyazacytidine induced miR-217 expression and downregulated KLK7 in EACC; deoxyazacytidine also attenuated CSC-mediated miR-217 repression and upregulation of KLK7 in IEE and EACC. Overexpression of miR-217 significantly decreased, whereas overexpression of KLK7 increased proliferation, invasion and tumorigenicity of EACC. Collectively, these data demonstrate that epigenetic repression of miR-217 contributes to the pathogenesis of EAC via upregulation of KLK7 and suggest that restoration of miR-217 expression may be a novel treatment strategy for these malignancies.

Abstract 935: Lung cancer metabolomics identifies metabolites as robust risk biomarkers

Lung cancer is a major health burden on the general population, as it will kill 160,000 people annually in the US, making it the number one cause of cancer related deaths. The prognosis for lung cancer is still very poor, with fewer than 15% of patients surviving 5 years after primary diagnosis, indicating the enormous necessity to search for biomarkers for early lung cancer detection when amenable to treatment. Currently accepted methods for early detection of lung cancer are limited to low-dose spiral CT (LDCT) scanning in high-risk populations. However, the specificity of LDCT is low, with a false positive rate of 96%. Our goal is to identify stable and reproducible biomarkers in non-invasively collected biofluids, namely urine, that may be powerful risk assessment screening tools. To that extent, we first conducted a first of its kind effort using mass spectrometry-based untargeted metabolic profiling of urine samples from 469 lung cancer patients and 536 healthy population controls in the NCI-MD case-control study, We found four metabolites to be independent and robust classifiers of lung cancer diagnosis and prognosis: novel and previously un-described creatine riboside, N-acetylneuraminic acid (NANA), cortisol sulfate and a metabolite with a mass to charge ratio of 561 detected in electrospray ionization (ESI) positive mode. Furthermore, creatine riboside and NANA were also found to be elevated in 48 stage I lung tumors matched to adjacent non-tumor tissues, linking them directly to deregulated tumor metabolism. The next step was to assess whether these metabolites are elevated in subjects prior to lung cancer diagnosis. To that end, we analyzed the urine of 180 patients and 349 non-diseased controls from the prospective Southern Community Cohort Study (SCCS). Controls were individually matched to cases in a 2:1 ratio using incidence density sampling by age (+/- 2 years), sex, race, recruitment site, menopausal status (women), and date of sample collection (+/- 6 months). We confirmed that two of the four metabolites, creatine riboside and NANA were associated with lung cancer risk with smoking-adjusted Odds Ratios (OR) of 1.8 and 1.5, respectively (P &lt;0.02). These metabolites, having been observed as deregulated in tumor metabolism, may become interesting targets for future studies regarding therapeutic interventions. The associations with risk were stronger among European than African Americans, and among whites were observed in individuals having been diagnosed within two years of cohort enrollment (OR = 2.7 and 2.5, respectively, for creatine riboside and NANA; P = 0.004) and two or more years after cohort enrollment (OR = 3.6 and 3.3, respectively; P = 0.02). These results provide strong preliminary data that identified metabolite biomarkers have a potential utility as clinical screening tools for early diagnosis of lung cancer, when prognosis is significantly better.

Citation Format: Majda Haznadar, Qiuyin Cai, Kristopher W. Krausz, Elise D. Bowman, William J. Blot, Frank J. Gonzalez, Curtis C. Harris. Lung cancer metabolomics identifies metabolites as robust risk biomarkers. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 935. doi:10.1158/1538-7445.AM2015-935

Abstract LB-173: The Thailand initiative in genomics and expression research for liver cancer (TIGER-LC): Defining novel subtypes of hepatocellular carcinoma and cholangiocarcinoma

Hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA) represent two major histological cancer subtypes confined within the liver. They are clinically and biologically heterogeneous, and are highly resistant to treatment, which makes them the second most lethal cancer for men in the world. In Thailand, liver cancer represents the primary cause of cancer-related death and is a major health problem, especially in north-eastern area of Thailand where liver fluke (O. viverrini) is endemic and approximately 70% of liver cancers are CCA. While HBV and HCV are major etiological factors for HCC globally, liver fluke infection is a major etiological factor for CCA in Thailand. These unique risk factor patterns provide an opportunity to study cancer heterogeneity and its unique tumor biology. The Thailand Initiative in Genomics and Expression Research for Liver Cancer (TIGER-LC) consortium was established to identify genomic and expression factors that may modify HCC and CCA susceptibility and progression. In a Phase I study, we determined molecular subtypes of HCC and CCA. We performed genomic profiling of 398 surgical specimens derived from 199 liver cancer patients. We employed the Affymetrix Human Transcriptome Array 2.0 to examine transcriptome profiles. Unsupervised Consensus Clustering (cCluster), Subclass Mapping (SM) and Gene Set Enrichment Analysis (GSEA) algorithms were used to analyze transcriptome data. The results were validated in 247 Asian HCC cases and 104 Caucasian CCA cases. We found that the Thai HCC cases consisted of 3 stable subgroups (C1-C3), while the Thai CCA cases contained 4 stable subgroups (C1-C4) based on gene expression patterns determined by cCluster. SM analysis revealed that CCA-C1 and HCC-C1 subtypes shared a similar gene expression matrix, as did CCA-C2 and HCC-C2 for a separate pattern. Interestingly, patients in both CCA-C1 and HCC-C1 had a poor prognosis, while those in CCA-C2 and HCC-C2 had a good prognosis. These prognostic subtypes were validated in an independent Asian HCC cohort but not in a Caucasian CCA cohort. GSEA revealed that among 17 significantly altered canonical pathways in the C1 subtype, 8 are related to mitotic checkpoint signaling. In contrast, the main signaling pathways associated with the C2 subtype were related to cytokine and chemokine signaling. We found that certain mitotic checkpoint genes are highly activated only in C1, but not in the C2 subtype. These results are consistent with the hypothesis that CCA and HCC from Asian populations consist of molecularly-similar tumor subgroups with similar prognostic impacts and unique tumor biology and that the C1 subtype may be sensitive to mitotic checkpoint blockage. Our ability to rigorously classify and validate both HCC and CCA using these tools may represent a new avenue for the development of targeted therapeutic interventions.

Citation Format: The TIGER-LC Consortium, Jittiporn Chaisaingmongkol, Anuradha Budhu, Hien Dang, Siritida Rabibhadana, Benjarath Pupacdi, Marshonna Forgues, Vajarabhongsa Bhudhisawasdi, Nirush Lertprasertsuke, Anon Chotirosniramit, Chawalit Pairojkul, Chirayu U. Auewarakul, Thaniya Sricharunrat, Kannika Phornphutkul, Suleeporn Sangrajrang, Maggie Cam, Ping He, Stephen M. Hewitt, Xiaolin Wu, Snorri S. Thorgeirsson, Paul S. Meltzer, Christopher A. Loffredo, Robert H. Wiltrout, Curtis C. Harris, Chulabhorn Mahidol, Mathuros Ruchirawat, Xin W. Wang. The Thailand initiative in genomics and expression research for liver cancer (TIGER-LC): Defining novel subtypes of hepatocellular carcinoma and cholangiocarcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-173. doi:10.1158/1538-7445.AM2015-LB-173

Increased microRNA-34b and -34c predominantly expressed in stromal tissues is associated with poor prognosis in human colon cancer

The microRNA-34 family (miR-34a, -34b and -34c) have been reported to be tumor suppressor microRNAs (miRNAs) that are regulated by the TP53 and DNA hypermethylation. However, the expression, regulation, and prognostic value of the miR-34 family have not been systematically studied in colon cancer. To elucidate the roles of miR-34 family in colon carcinogenesis, miR-34a/b/c were measured in tumors and adjacent noncancerous tissues from 159 American and 113 Chinese colon cancer patients using quantitative RT-PCR, and we examined associations between miR-34a/b/c expression with TNM staging, cancer-specific mortality, TP53 mutation status and Affymetrix microarray data. All miR-34 family members were significantly increased in colon tumors, counter to the proposed tumor suppressor role for these miRNAs. Increased miR-34b/c were observed in more advanced tumors in two independent cohorts and increased expression of miR-34b/c was associated with poor cancer-specific mortality. While the expression of miR-34 family was not associated with TP53 mutation status, TP53 transcriptional activity was associated with miR-34a/b/c expression that is consistent with the proposed regulation of miR-34a/b/c by TP53. To examine where the miR-34 family is expressed, the expression of miR-34 family was compared between epitheliums and stromal tissues using laser microdissection technique. The expression of miR-34b/c was increased significantly in stromal tissues, especially in cancer stroma, compared with epithelial tissue. In conclusion, increased miR-34b/c predominantly expressed in stromal tissues is associated with poor prognosis in colon cancer. MiR-34 may contribute to cancer-stromal interaction associated with colon cancer progression.

Expression and clinical significance of genes frequently mutated in small cell lung cancers defined by whole exome/RNA sequencing

Small cell lung cancer (SCLC) is the most aggressive type of lung cancer. Only 15% of SCLC patients survive beyond 2 years after diagnosis. Therefore, for the improvement of patients' outcome in this disease, it is necessary to identify genetic alterations applicable as therapeutic targets in SCLC cells. The purpose of this study is the identification of genes frequently mutated and expressed in SCLCs that will be targetable for therapy of SCLC patients. Exome sequencing was performed in 28 primary tumors and 16 metastatic tumors from 38 patients with SCLCs. Expression of mutant alleles was verified in 19 cases by RNA sequencing. TP53, RB1 and PTEN were identified as being significantly mutated genes. Additional 36 genes were identified as being frequently (≥10%) mutated in SCLCs by combining the results of this study and two recent studies. Mutated alleles were expressed in 8 of the 36 genes, TMEM132D, SPTA1, VPS13B, CSMD2, ANK2, ASTN1, ASPM and FBN3. In particular, the TMEM132D, SPTA1 and VPS13B genes were commonly mutated in both early and late stage tumors, primary tumors and metastases, and tumors before and after chemotherapy, as in the case of the TP53 and RB1 genes. Therefore, in addition to TP53, RB1 and PTEN, TMEM132D, SPTA1 and VPS13B could be also involved in SCLC development, with the products from their mutated alleles being potential therapeutic targets in SCLC patients.

Prognostic significance and molecular features of signet-ring cell and mucinous components in colorectal carcinoma

BACKGROUND

Colorectal carcinoma (CRC) represents a group of histopathologically and molecularly heterogeneous diseases, which may contain signet-ring cell component and/or mucinous component to a varying extent under pathology assessment. However, little is known about the prognostic significance of those components, independent of various tumor molecular features.

METHODS

Utilizing a molecular pathological epidemiology database of 1,336 rectal and colon cancers in the Nurses' Health Study and the Health Professionals Follow-up Study, we examined patient survival according to the proportion of signet-ring cell and mucinous components in CRCs. Cox proportional hazards models were used to compute hazard ratio (HR) for mortality, adjusting for potential confounders including stage, microsatellite instability, CpG island methylator phenotype, LINE-1 methylation, and KRAS, BRAF, and PIK3CA mutations.

RESULTS

Compared to CRC without signet-ring cell component, 1-50 % signet-ring cell component was associated with multivariate CRC-specific mortality HR of 1.40 [95 % confidence interval (CI) 1.02-1.93], and >50 % signet-ring cell component was associated with multivariate CRC-specific mortality HR of 4.53 (95 % CI 2.53-8.12) (P trend < 0.0001). Compared to CRC without mucinous component, neither 1-50 % mucinous component (multivariate HR 1.04; 95 % CI 0.81-1.33) nor >50 % mucinous component (multivariate HR 0.82; 95 % CI 0.54-1.23) was significantly associated with CRC-specific mortality (P trend < 0.57).

CONCLUSIONS

Even a minor (50 % or less) signet-ring cell component in CRC was associated with higher patient mortality, independent of various tumor molecular and other clinicopathological features. In contrast, mucinous component was not associated with mortality in CRC patients.

Telomere length variation: A potential new telomere biomarker for lung cancer risk

OBJECTIVES

In this report the associations between telomere length variation (TLV), mean telomere length in blood lymphocytes and lung cancer risk were examined.

MATERIALS AND METHODS

The study design is case-control. Cases (N=191) were patients newly diagnosed with histologically confirmed non-small cell lung cancer. Controls (N=207) were healthy individuals recruited from the same counties as cases and matched to cases on age and gender. Telomere fluorescent in situ hybridization was used to measure telomere features using short-term cultured blood lymphocytes. Logistic regression was used to estimate the strength of association between telomere features and lung cancer risk.

RESULTS

Telomere length variation across all chromosomal ends was significantly associated with lung cancer risk; adjusted odds ratios 4.67 [95% confidence interval (CI): 1.46-14.9] and 0.46 (95% CI: 0.25-0.84) for younger (age≤60) and older (age>60) individuals, respectively. TLV and mean telomere length jointly affected lung cancer risk: when comparing individuals with short telomere length and high TLV to those with long telomere length and low TLV, adjusted odd ratios were 8.21 (95% CI: 1.71-39.5) and 0.33 (95% CI: 0.15-0.72) for younger and older individuals, respectively.

CONCLUSIONS

TLV in blood lymphocytes is significantly associated with lung cancer risk and the associations were modulated by age. TLV in combination with mean telomere length might be useful in identifying high risk population for lung cancer computerized tomography screening.

Characterization of large structural genetic mosaicism in human autosomes

Analyses of genome-wide association study (GWAS) data have revealed that detectable genetic mosaicism involving large (>2 Mb) structural autosomal alterations occurs in a fraction of individuals. We present results for a set of 24,849 genotyped individuals (total GWAS set II [TGSII]) in whom 341 large autosomal abnormalities were observed in 168 (0.68%) individuals. Merging data from the new TGSII set with data from two prior reports (the Gene-Environment Association Studies and the total GWAS set I) generated a large dataset of 127,179 individuals; we then conducted a meta-analysis to investigate the patterns of detectable autosomal mosaicism (n = 1,315 events in 925 [0.73%] individuals). Restricting to events >2 Mb in size, we observed an increase in event frequency as event size decreased. The combined results underscore that the rate of detectable mosaicism increases with age (p value = 5.5 × 10(-31)) and is higher in men (p value = 0.002) but lower in participants of African ancestry (p value = 0.003). In a subset of 47 individuals from whom serial samples were collected up to 6 years apart, complex changes were noted over time and showed an overall increase in the proportion of mosaic cells as age increased. Our large combined sample allowed for a unique ability to characterize detectable genetic mosaicism involving large structural events and strengthens the emerging evidence of non-random erosion of the genome in the aging population.

Identification of a metastasis-specific MicroRNA signature in human colorectal cancer

BACKGROUND

Distant metastasis is the major cause of mortality in colorectal cancer (CRC). We performed a systemic, comprehensive discovery for expression patterns of metastasis-specific microRNAs (miRNAs) by directly comparing primary CRCs (pCRCs) and matched liver metastases (LMs) and evaluated the feasibility of their clinical application as metastasis-specific biomarkers.

METHODS

CRC metastasis-specific miRNA profiles were generated by analyzing nine pairs of pCRC and LM tissues, followed by quantitative validation in an independent cohort of 58 pairs of matched pCRC and LM tissues. We evaluated associations between miRNA expression and patient survival and ability to predict metastasis in another 84 patients with CRC. Subsequently, associations were quantitatively validated in 175 CRC tissues and 169 serum samples. Kaplan-Meier, Cox regression, and logistic regression analyses were used. All statistical tests were two-sided.

RESULTS

Twenty-three miRNAs were identified that were differentially expressed between pCRC and LM (P < .001; FDR < .5). Four miRNAs downregulated in LM (let-7i, miR-10b, miR-221, and miR-320a) and one upregulated miR (miR-885-5p) were quantitatively validated in pCRC (P < .0001). Low let-7i expression in pCRC tissue predicted worsened prognosis (hazard ratio [HR] = 5.0, 95% confidence interval [CI] = 1.0 to 24.4, P = .0479) as well as distant metastasis (odds ratio [OR] = 5.5, 95% CI = 1.1 to 26.8, P = .0334). High miR-10b expression in pCRC tissue independently predicted distant metastasis (OR = 4.9, 95% CI = 1.2 to 19.7, P = .0248). High serum miR-885-5p expression independently predicted prognosis (HR = 2.9, 95% CI = 1.1 to 7.5, P = .0323), LN metastasis (OR = 3.0, 95% CI = 1.3 to 7.2, P = .0116), and distant metastasis (OR = 3.1, 95% CI = 1.0 to 10.0, P = .0456), whereas tissue miR-885-5p expression did not. Expression patterns of miRNAs were confirmed by in situ hybridization.

CONCLUSIONS

We discovered a metastasis-specific miRNA signature in pCRCs and discovered novel tissue- and serum-based CRC metastasis-specific miRNA biomarkers through intensive validation. These unique miRNAs may be clinically applicable to predict prognosis and distant metastasis in CRC.