Prognostic association of PTGS2 (COX-2) over-expression according to BRAF mutation status in colorectal cancer: Results from two prospective cohorts and CALGB 89803 (Alliance) trial

BACKGROUND

Prostaglandin-endoperoxide synthase 2 (PTGS2, cyclooxygenase-2, COX-2)-prostaglandin E2 (PGE2) pathway promotes tumour progression. Considering evidence suggesting increased PGE2 synthesis by BRAF mutation in tumour cells, we hypothesised that the association of tumour PTGS2 (COX-2) expression with colorectal cancer mortality might be stronger in BRAF-mutated tumours than in BRAF-wild-type tumours.

METHODS

Using 1708 patients, including 1200 stage I-IV colorectal carcinoma cases in the Nurses' Health Study (NHS) and the Health Professionals Follow-up Study (HPFS) and 508 stage III colon cancer cases in a National Cancer Institute-sponsored randomised controlled trial of adjuvant therapy (CALGB/Alliance 89803), we evaluated tumour PTGS2 (COX-2) expression status using immunohistochemistry. We examined the prognostic association of PTGS2 (COX-2) expression in strata of BRAF mutation status by multivariable Cox proportional hazards regression models to adjust for potential confounders, including disease stage, tumour differentiation, microsatellite instability status and KRAS and PIK3CA mutations.

RESULTS

In NHS and HPFS, the association of PTGS2 (COX-2) expression with colorectal cancer-specific survival differed by BRAF mutation status (Pinteraction = 0.0005); compared with PTGS2 (COX-2)-negative/low carcinomas, the multivariable-adjusted hazard ratios for PTGS2 (COX-2)-high carcinomas were 2.44 (95% confidence interval, 1.39-4.28) in BRAF-mutated cases and 0.82 (95% confidence interval, 0.65-1.04) in BRAF-wild-type cases. Differential prognostic associations of PTGS2 (COX-2) expression in strata of BRAF mutation status were similarly observed in CALGB/Alliance 89803 trial (Pinteraction = 0.03).

CONCLUSIONS

The association of tumour PTGS2 (COX-2) expression with colorectal cancer mortality is stronger in BRAF-mutated tumours than in BRAF-wild-type tumours, supporting interactive roles of PTGS2 (COX-2) expression and BRAF mutation statuses in prognostication of patients with colorectal cancer; ClinicalTrials.gov Identifier, NCT00003835.

Oxytocin levels and sex differences in autism spectrum disorder with severe intellectual disabilities

There were few reports of oxytocin (OXT) concentrations of autism spectrum disorder (ASD) patients with severe intellectual disabilities. We measured serum OXT concentrations in 79 hospitalized patients with severe intellectual disabilities (16-60 years old, 50 males and 29 females, 54 ASD patients) and investigated the associations between serum OXT concentration, symptom scores, sex differences, and autism spectrum disorder. There were no significant effects of diagnosis, severity of intellectual disabilities, and total score of the Japanese version of the Aberrant Behavior Checklist (ABC-J), the Childhood Autism Rating Scale-Tokyo Version (CARS-TV), and the Japanese version of the Repetitive Behavior Scale-Revised (RBS-R). However, there were sex differences in the correlations between OXT concentrations and subscale scores in the ASD group. The male ASD group (n = 39) showed negative correlations between RBS-R Self-injurious and Sameness subscale scores and serum OXT concentrations. In the female ASD group(n = 15), CARS-TV Nonverbal communication subscale scores and RBS-R Compulsive subscale scores were seen to positively correlate with serum OXT concentrations. These findings suggest that OXT functions differ in males and females with severe intellectual disabilities and that OXT partly affects autism and related to some of the repetitive behaviors and nonverbal communication, in ASD patients with severe intellectual disabilities.

Calcium Intake and Risk of Colorectal Cancer According to Tumor-infiltrating T Cells

Calcium intake has been associated with a lower risk of colorectal cancer. Calcium signaling may enhance T-cell proliferation and differentiation, and contribute to T-cell-mediated antitumor immunity. In this prospective cohort study, we investigated the association between calcium intake and colorectal cancer risk according to tumor immunity status to provide additional insights into the role of calcium in colorectal carcinogenesis. The densities of tumor-infiltrating T-cell subsets [CD3⁺, CD8⁺ , CD45RO (PTPRC) ⁺ , or FOXP3⁺ cell] were assessed using IHC and computer-assisted image analysis in 736 cancer cases that developed among 136,249 individuals in two cohorts. HRs and 95% confidence intervals (CI) were calculated using Cox proportional hazards regression. Total calcium intake was associated with a multivariable HR of 0.55 (comparing ≥1,200 vs. <600 mg/day; 95% CI, 0.36-0.84; P _trend = 0.002) for CD8⁺ T-cell-low but not for CD8⁺ T-cell-high tumors (HR = 1.02; 95% CI, 0.67-1.55; P _trend = 0.47). Similarly, the corresponding HRs (95% CIs) for calcium for low versus high T-cell-infiltrated tumors were 0.63 (0.42-0.94; P _trend = 0.01) and 0.89 (0.58-1.35; P _trend = 0.20) for CD3⁺ ; 0.58 (0.39-0.87; P _trend = 0.006) and 1.04 (0.69-1.58; P _trend = 0.54) for CD45RO⁺ ; and 0.56 (0.36-0.85; P _trend = 0.006) and 1.10 (0.72-1.67; P _trend = 0.47) for FOXP3⁺ , although the differences by subtypes defined by T-cell density were not statistically significant. These potential differential associations generally appeared consistent regardless of sex, source of calcium intake, tumor location, and tumor microsatellite instability status. Our findings suggest a possible role of calcium in cancer immunoprevention via modulation of T-cell function.

Insights into Pathogenic Interactions Among Environment, Host, and Tumor at the Crossroads of Molecular Pathology and Epidemiology

Evidence indicates that diet, nutrition, lifestyle, the environment, the microbiome, and other exogenous factors have pathogenic roles and also influence the genome, epigenome, transcriptome, proteome, and metabolome of tumor and nonneoplastic cells, including immune cells. With the need for big-data research, pathology must transform to integrate data science fields, including epidemiology, biostatistics, and bioinformatics. The research framework of molecular pathological epidemiology (MPE) demonstrates the strengths of such an interdisciplinary integration, having been used to study breast, lung, prostate, and colorectal cancers. The MPE research paradigm not only can provide novel insights into interactions among environment, tumor, and host but also opens new research frontiers. New developments-such as computational digital pathology, systems biology, artificial intelligence, and in vivo pathology technologies-will further transform pathology and MPE. Although it is necessary to address the rarity of transdisciplinary education and training programs, MPE provides an exemplary model of integrative scientific approaches and contributes to advancements in precision medicine, therapy, and prevention.

Physical Activity and Colorectal Cancer Prognosis According to Tumor-Infiltrating T Cells

Background

Evidence suggests that high-level physical activity may potentially reduce cancer mortality through its immune enhancement effect. We therefore hypothesized that survival benefits associated with physical activity might be stronger in colorectal carcinomas with lower immune reaction at diagnosis.

Methods

Using molecular pathological epidemiology databases of 470 colon and rectal carcinoma cases in the Nurses’ Health Study and the Health Professionals Follow-up Study, we assessed the prognostic association of postdiagnosis physical activity in strata of densities of CD3⁺ cells, CD8⁺ cells, CD45RO (PTPRC)⁺ cells, or FOXP3⁺ cells in tumor tissue. Cox proportional hazards regression model was used to adjust for potential confounders, including microsatellite instability, CpG island methylator phenotype, long interspersed nucleotide element-1 methylation, KRAS, BRAF, and PIK3CA mutations, and expression of CTNNB1 (beta-catenin), PTGS2 (cyclooxygenase-2), and IRS1.

Results

The association of postdiagnosis physical activity with colorectal cancer-specific mortality differed by CD3⁺ cell density (P_interaction < .001). Multivariable-adjusted colorectal cancer-specific mortality hazard ratios for a quartile-unit increase in physical activity were 0.56 (95% confidence interval = 0.38 to 0.83) among cases with the lowest quartile of CD3⁺ cell density compared with 1.14 (95% confidence interval = 0.79 to 1.65) in cases with the highest quartile. We observed no differential survival association of physical activity by densities of CD8⁺ cells, CD45RO⁺ cells, or FOXP3⁺ cells.

Conclusions

The association between postdiagnosis physical activity and colorectal cancer survival appeared stronger for carcinomas with lower T cell infiltrates, suggesting an interactive effect of exercise and immunity on colorectal cancer progression.

Smoking and Risk of Colorectal Cancer Sub-Classified by Tumor-Infiltrating T Cells

Background

Evidence indicates not only carcinogenic effect of cigarette smoking but also its immunosuppressive effect. We hypothesized that the association of smoking with colorectal cancer risk might be stronger for tumors with lower anti-tumor adaptive immune response.

Methods

During follow-up of 134 981 participants (3 490 851 person-years) in the Nurses' Health Study and Health Professionals Follow-up Study, we documented 729 rectal and colon cancer cases with available data on T-cell densities in tumor microenvironment. Using the duplication-method Cox regression model, we examined a differential association of smoking status with risk of colorectal carcinoma subclassified by densities of CD3+ cells, CD8+ cells, CD45RO (PTPRC)+ cells, or FOXP3+ cells. All statistical tests were two-sided.

Results

The association of smoking status with colorectal cancer risk differed by CD3+ cell density (Pheterogeneity = .007). Compared with never smokers, multivariable-adjusted hazard ratios for CD3+ cell-low colorectal cancer were 1.38 (95% confidence interval = 1.09 to 1.75) in former smokers and 1.59 (95% confidence interval = 1.14 to 2.23) in current smokers (Ptrend = .002, across smoking status categories). In contrast, smoking status was not associated with CD3+ cell-high cancer risk (Ptrend = .52). This differential association appeared consistent in strata of microsatellite instability, CpG island methylator phenotype, or BRAF mutation status. There was no statistically significant differential association according to densities of CD8+ cells, CD45RO+ cells, or FOXP3+ cells (Pheterogeneity > .04, with adjusted α of 0.01).

Conclusions

Colorectal cancer risk increased by smoking was stronger for tumors with lower T-lymphocyte response, suggesting an interplay of smoking and immunity in colorectal carcinogenesis.

SMAD4 Loss in Colorectal Cancer Patients Correlates with Recurrence, Loss of Immune Infiltrate, and Chemoresistance

PURPOSE

SMAD4 has shown promise in identifying patients with colorectal cancer at high risk of recurrence or death.Experimental Design: A discovery cohort and independent validation cohort were classified by SMAD4 status. SMAD4 status and immune infiltrate measurements were tested for association with recurrence-free survival (RFS). Patient-derived xenografts from SMAD4-deficient and SMAD4-retained tumors were used to examine chemoresistance.

RESULTS

The discovery cohort consisted of 364 patients with stage I-IV colorectal cancer. Median age at diagnosis was 53 years. The cohort consisted of 61% left-sided tumors and 62% stage II/III patients. Median follow-up was 5.4 years (interquartile range, 2.3-8.2). SMAD4 loss, noted in 13% of tumors, was associated with higher tumor and nodal stage, adjuvant therapy use, fewer tumor-infiltrating lymphocytes (TIL), and lower peritumoral lymphocyte aggregate (PLA) scores (all P < 0.04). SMAD4 loss was associated with worse RFS (P = 0.02). When stratified by SMAD4 and immune infiltrate status, patients with SMAD4 loss and low TIL or PLA had worse RFS (P = 0.002 and P = 0.006, respectively). Among patients receiving 5-fluorouracil (5-FU)-based systemic chemotherapy, those with SMAD4 loss had a median RFS of 3.8 years compared with 13 years for patients with SMAD4 retained. In xenografted mice, the SMAD4-lost tumors displayed resistance to 5-FU. An independent cohort replicated our findings, in particular, the association of SMAD4 loss with decreased immune infiltrate, as well as worse disease-specific survival.

CONCLUSIONS

Our data show SMAD4 loss correlates with worse clinical outcome, resistance to chemotherapy, and decreased immune infiltrate, supporting its use as a prognostic marker in patients with colorectal cancer.

The Amount of Bifidobacterium Genus in Colorectal Carcinoma Tissue in Relation to Tumor Characteristics and Clinical Outcome

Evidence indicates a complex link between microbiota, tumor characteristics, and host immunity in the tumor microenvironment. In experimental studies, bifidobacteria appear to modulate intestinal epithelial cell differentiation. Accumulating evidence suggests that bifidobacteria may enhance the antitumor immunity and efficacy of immunotherapy. We hypothesized that the amount of bifidobacteria in colorectal carcinoma tissue might be associated with tumor differentiation and higher immune response to colorectal cancer. Using a molecular pathologic epidemiology database of 1313 rectal and colon cancers, we measured the amount of Bifidobacterium DNA in carcinoma tissue by a quantitative PCR assay. The multivariable regression model was used to adjust for potential confounders, including microsatellite instability status, CpG island methylator phenotype, long-interspersed nucleotide element-1 methylation, and KRAS, BRAF, and PIK3CA mutations. Intratumor bifidobacteria were detected in 393 cases (30%). The amount of bifidobacteria was associated with the extent of signet ring cells (P = 0.002). Compared with Bifidobacterium-negative cases, multivariable odd ratios for the extent of signet ring cells were 1.29 (95% CI, 0.74-2.24) for Bifidobacterium-low cases and 1.87 (95% CI, 1.16-3.02) for Bifidobacterium-high cases (Ptrend = 0.01). The association between intratumor bifidobacteria and signet ring cells suggests a possible role of bifidobacteria in determining distinct tumor characteristics or as an indicator of dysfunctional mucosal barrier in colorectal cancer.

Vitamin D status after colorectal cancer diagnosis and patient survival according to immune response to tumour

BACKGROUND

High-level plasma 25-hydroxyvitamin D [25(OH)D] has been associated with lower colorectal cancer incidence and mortality. Considering evidence indicating immunomodulatory effects of vitamin D, we hypothesised that survival benefits from high systemic vitamin D level might be stronger for colorectal carcinoma with lower immune response to tumour.

METHODS

Using 869 colon and rectal cancer cases within the Nurses' Health Study and Health Professionals Follow-up Study, we assessed the prognostic association of postdiagnosis 25(OH)D score [derived from diet and lifestyle variables to predict plasma 25(OH)D level] in strata of levels of histopathologic lymphocytic reaction. The Cox proportional hazards regression model was adjusted for potential confounders, including microsatellite instability, CpG island methylator phenotype, LINE-1 methylation, PTGS2 (cyclooxygenase-2) expression and KRAS, BRAF and PIK3CA mutations.

RESULTS

The association of postdiagnosis 25(OH)D score with colorectal cancer-specific mortality differed by levels of peritumoural lymphocytic reaction (pinteraction = 0.001). Multivariable-adjusted mortality hazard ratios for a quintile-unit increase of 25(OH)D score were 0.69 [95% confidence interval (CI), 0.54-0.89] in cases with negative/low peritumoural lymphocytic reaction, 1.08 (95% CI, 0.93-1.26) in cases with intermediate peritumoural reaction and 1.25 (95% CI, 0.75-2.09) in cases with high peritumoural reaction. The survival association of the 25(OH)D score did not significantly differ by Crohn's-like lymphoid reaction, intratumoural periglandular reaction or tumour-infiltrating lymphocytes.

CONCLUSIONS

The association between the 25(OH)D score and colorectal cancer survival is stronger for carcinomas with lower peritumoural lymphocytic reaction. Our results suggesting interactive effects of vitamin D and immune response may contribute to personalised dietary and lifestyle intervention strategies.

Diets That Promote Colon Inflammation Associate With Risk of Colorectal Carcinomas That Contain Fusobacterium nucleatum

BACKGROUND & AIMS

Specific nutritional components are likely to induce intestinal inflammation, which is characterized by increased levels of interleukin 6 (IL6), C-reactive protein (CRP), and tumor necrosis factor-receptor superfamily member 1B (TNFRSF1B) in the circulation and promotes colorectal carcinogenesis. The inflammatory effects of a diet can be estimated based on an empiric dietary inflammatory pattern (EDIP) score, calculated based on intake of 18 foods associated with plasma levels of IL6, CRP, and TNFRSF1B. An inflammatory environment in the colon (based on increased levels of IL6, CRP, and TNFRSF1B in peripheral blood) contributes to impairment of the mucosal barrier and altered immune cell responses, affecting the composition of the intestinal microbiota. Colonization by Fusobacterium nucleatum has been associated with the presence and features of colorectal adenocarcinoma. We investigated the association between diets that promote inflammation (based on EDIP score) and colorectal cancer subtypes classified by level of F nucleatum in the tumor microenvironment.

METHODS

We calculated EDIP scores based on answers to food frequency questionnaires collected from participants in the Nurses' Health Study (through June 1, 2012) and the Health Professionals Follow-up Study (through January 31, 2012). Participants in both cohorts reported diagnoses of rectal or colon cancer in biennial questionnaires; deaths from unreported colorectal cancer cases were identified through the National Death Index and next of kin. Colorectal tumor tissues were collected from hospitals where the patients underwent tumor resection and F nucleatum DNA was quantified by a polymerase chain reaction assay. We used multivariable duplication-method Cox proportional hazard regression to assess the associations of EDIP scores with risks of colorectal cancer subclassified by F nucleatum status.

RESULTS

During 28 years of follow-up evaluation of 124,433 participants, we documented 951 incident cases of colorectal carcinoma with tissue F nucleatum data. Higher EDIP scores were associated with increased risk of F nucleatum-positive colorectal tumors (P_trend = .03); for subjects in the highest vs lowest EDIP score tertiles, the hazard ratio for F nucleatum-positive colorectal tumors was 1.63 (95% CI, 1.03-2.58). EDIP scores did not associate with F nucleatum-negative tumors (P_trend = .44). High EDIP scores associated with proximal F nucleatum-positive colorectal tumors but not with proximal F nucleatum-negative colorectal tumors (P_{heterogeneity} = .003).

CONCLUSIONS

Diets that may promote intestinal inflammation, based on EDIP score, are associated with increased risk of F nucleatum-positive colorectal carcinomas, but not carcinomas that do not contain these bacteria. These findings indicate that diet-induced intestinal inflammation alters the gut microbiome to contribute to colorectal carcinogenesis; nutritional interventions might be used in precision medicine and cancer prevention.

Continuity of transcriptomes among colorectal cancer subtypes based on meta-analysis

BACKGROUND

Previous approaches to defining subtypes of colorectal carcinoma (CRC) and other cancers based on transcriptomes have assumed the existence of discrete subtypes. We analyze gene expression patterns of colorectal tumors from a large number of patients to test this assumption and propose an approach to identify potentially a continuum of subtypes that are present across independent studies and cohorts.

RESULTS

We examine the assumption of discrete CRC subtypes by integrating 18 published gene expression datasets and > 3700 patients, and contrary to previous reports, find no evidence to support the existence of discrete transcriptional subtypes. Using a meta-analysis approach to identify co-expression patterns present in multiple datasets, we identify and define robust, continuously varying subtype scores to represent CRC transcriptomes. The subtype scores are consistent with established subtypes (including microsatellite instability and previously proposed discrete transcriptome subtypes), but better represent overall transcriptional activity than do discrete subtypes. The scores are also better predictors of tumor location, stage, grade, and times of disease-free survival than discrete subtypes. Gene set enrichment analysis reveals that the subtype scores characterize T-cell function, inflammation response, and cyclin-dependent kinase regulation of DNA replication.

CONCLUSIONS

We find no evidence to support discrete subtypes of the CRC transcriptome and instead propose two validated scores to better characterize a continuity of CRC transcriptomes.

Fusobacterium nucleatum in Colorectal Cancer Relates to Immune Response Differentially by Tumor Microsatellite Instability Status

The presence of Fusobacterium nucleatum (F. nucleatum) in colorectal carcinoma tissue has been associated with microsatellite instability (MSI), lower-level T-cell infiltrates, and poor clinical outcomes. Considering differences in the tumor-immune microenvironment between MSI-high and non-MSI-high carcinomas, we hypothesized that the association of F. nucleatum with immune response might differ by tumor MSI status. Using samples from 1,041 rectal and colon cancer patients within the Nurses' Health Study and Health Professionals Follow-up Study, we measured F. nucleatum DNA in tumor tissue by a quantitative polymerase chain reaction assay. Multivariable logistic regression models were used to examine the association between F. nucleatum status and histopathologic lymphocytic reactions or density of CD3⁺ cells, CD8⁺ cells, CD45RO (PTPRC)⁺ cells, or FOXP3⁺ cells in strata of tumor MSI status. We adjusted for potential confounders, including CpG island methylator phenotype; LINE-1 methylation; and KRAS, BRAF, and PIK3CA mutations. The association of F. nucleatum with tumor-infiltrating lymphocytes (TIL) and intratumoral periglandular reaction differed by tumor MSI status (P _interaction = 0.002). The presence of F. nucleatum was negatively associated with TIL in MSI-high tumors [multivariable odds ratio (OR), 0.45; 95% confidence interval (CI), 0.22-0.92], but positively associated with TIL in non-MSI-high tumors (multivariable OR 1.91; 95% CI, 1.12-3.25). No significant differential association was observed for peritumoral lymphocytic reaction, Crohn-like lymphoid reaction, or T-cell densities. In conclusion, the association of F. nucleatum with immune response to colorectal carcinoma differs by tumor MSI status, suggesting that F. nucleatum and MSI status interact to affect antitumor immune reactions. Cancer Immunol Res; 6(11); 1327-36. ©2018 AACR See related Spotlight on p. 1290.

Abstract PR03: Genetic mechanisms of immune evasion in colorectal cancer

Background: Immune checkpoint blockade has shown activity in microsatellite-instability high (MSI-H) colorectal cancers (CRCs). However, despite a very high mutational and neoantigen load among virtually all MSI-H tumors, the response rate is around 40-50%. In addition, for the majority of CRCs, which are microsatellite stable (MSS), immune checkpoint inhibitors have so far proven ineffective. Thus, to better understand the genetic drivers of immune evasion in CRC, we integrated next generation sequencing data from over 1200 tumors with transcriptional and immunohistochemical measures of immune infiltration.

Methods: We molecularly characterized 1,211 colorectal cancers, including 592 tumors from The Cancer Genome Atlas with whole exome sequencing (WES) and whole transcriptome (RNAseq) data and 619 cancers from two prospective cohort studies with WES and immunohistochemical (IHC) annotations. To identify driver gene alterations and their selection pressures specific to MSI-high tumors, we developed a statistical method to identify significantly mutated microsatellite tracts and we further developed a method to identify copy neutral loss of heterozygosity (CN-LOH) events. We used an established immune-gene transcriptional signature as well as IHC stains against specific subsets of immune-infiltrating cells to identify genetic events associated with immune evasion.

Results: We demonstrated that WNT-signaling and immune-related genes are significantly mutated in colorectal cancer. In MSI-H CRCs, we found biallelic antigen-presentation machinery (APM) mutations in the HLA Class I genes, B2M and TAP2, in addition to recurrent mutations in NLRC5 and RFX5, which downregulated HLA Class I expression. In all CRCs, we showed that WNT-signaling activity and APC-biallelic mutations are inversely associated with both transcriptional and IHC measures of T-cell infiltration. Specifically, nuclear CTNNB1 expression was inversely correlated with overall tumor-infiltrating lymphocytes (p = 0.027), CD8+ subset of T-cells (p = 0.0019) and CD45RO+ subset of T-cells (0.0080). Meanwhile, colorectal tumors with biallelic disruptive mutations in APC had a significantly decreased activated T-cell transcriptional signature (p = 4e-12) relative to samples with no disruptive mutations in APC. We further showed that in MSS tumors, AXIN2 (a key WNT-signaling effector) super-enhancer hypomethylation, independent of the APC mutation status, was further associated with decreased T-cell activity.

Conclusions: In this largest CRC genomic analysis to date, we identify genetic events that are associated with immune evasion in this disease. Specifically, we find evidence of immuno-editing in MSI-H tumors through disruptive mutations in APM. In the MSS and MSI-H subtype of CRCs, we use transcriptional and immunohistochemical orthogonal analyses to demonstrate exclusion of an effective immune infiltrate in CRC through an active WNT-signaling pathway. Our results shed light on the underlying molecular mechanisms of immune exclusion in CRC and have direct implications for novel combination immunotherapy trials for patients with this disease.

This abstract is also being presented as Poster B23.

Citation Format: Marios Giannakis, Catherine Grasso, Daniel Wells, Tsuyoshi Hamada, Xinmeng Jasmine Mu, Michael Quist, Jonathan Nowak, Reiko Nishihara, Charles M. Connolly, Sachet Shukla, William M. Grady, David Wheeler, Catherine J. Wu, Jesse Zaretsky, Levi Garraway, Thomas Hudson, Charles Fuchs, Antoni Ribas, Riki Peters, Shuji Ogino. Genetic mechanisms of immune evasion in colorectal cancer [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr PR03.

Calcium intake and risk of colorectal cancer according to expression status of calcium-sensing receptor (CASR)

OBJECTIVE

Although evidence suggests an inverse association between calcium intake and the risk of colorectal cancer, the mechanisms remain unclear. The calcium-sensing receptor (CASR) is expressed abundantly in normal colonic epithelium and may influence carcinogenesis. We hypothesized that calcium intake might be associated with lower risk of CASR-positive, but not CASR-negative, colorectal cancer.

DESIGN

We assessed tumour CASR protein expression using immunohistochemistry in 779 incident colon and rectal cancer cases that developed among 136 249 individuals in the Nurses' Health Study and Health Professionals Follow-Up Study. Duplication method Cox proportional hazards regression analysis was used to assess associations of calcium intake with incidence of colorectal adenocarcinoma subtypes by CASR status.

RESULTS

Total calcium intake was inversely associated with the risk of developing colorectal cancer (p_trend=0.01, comparing ≥1200 vs <600 mg/day: multivariable HR=0.75, 95% CI 0.60 to 0.95). For the same comparison, higher total calcium intake was associated with a lower risk of CASR-positive tumours (p_trend=0.003, multivariable HR=0.67, 95% CI 0.51 to 0.86) but not with CASR-negative tumours (p_trend=0.67, multivariable HR=1.15, 95% CI 0.75 to 1.78; p_{heterogeneity}=0.06 between the CASR subtypes). The stronger inverse associations of calcium intake with CASR-positive but not CASR-negative tumours generally appeared consistent regardless of sex, tumour location and source of calcium.

CONCLUSIONS

Our molecular pathological epidemiology data suggest a causal relationship between higher calcium intake and lower colorectal cancer risk, and a potential role of CASR in mediating antineoplastic effect of calcium.

Abstract 1228: Comparative genomic analysis of young-onset and late-onset colorectal cancer

Background: Young-onset colorectal cancer, the majority of which are sporadic, may have distinct molecular characteristics and etiologies. However, thus far, the genomic landscape of young-onset CRCs has remained largely uncharacterized. This study aimed to compare somatic mutation differences between young-onset and late-onset CRCs using the AACR GENIE data, a consortium of patients treated at 8 global cancer centers. Methods: Clinical and DNA mutation data on 2,081 CRC samples were downloaded from Sage Bionetworks (Synapse ID: syn7222066). A total of 162 samples from CRC patients who had more than one samples or were likely to have Lynch syndrome were excluded. Young-onset CRCs were defined as cancers arising at age &lt;50 years old while late-onset CRCs were defined as cancers arising at age ≥50 years old. Mutation rate per megabase (Mb) was calculated for each CRC and compared between groups by Wilcoxon rank sum test. The mutation frequency of each gene in young-onset and late-onset CRC was calculated separately for primary CRCs and metastatic CRCs. Mutation frequency differences between young- vs late-onset CRCs were tested by the Fisher's exact test with significance defined at the 5% alpha level. Results: Mutation data on 613 genes were analyzed on 955 primary and 676 metastatic CRCs. Overall, the most frequently mutated genes with a &gt;10% mutation frequency include: TP53 (66.86%), APC (59.46%), KRAS (47.42%), PIK3CA (18.40%), SMAD4 (12.71%) and BRAF (10.06%). The metastatic CRCs were on average slightly older than primary CRCs (mean age=56.96 vs. 55.90, two sample t test P=0.09). Comparing gene mutation between 300 young-onset versus 655 late-onset primary CRCs, mutation rate per Mb was slightly but not significantly higher in the latter (median=3.74 vs. 4.14, P=0.2199). DOT1L (9.82% vs. 1.95%, P=0.0014), IGF1R (6.12% vs. 1.72%, P=0.0057), BRCA1 (5.61% vs. 1.47%, P=0.0069), JUN (6.25% vs. 1.17%, P=0.0104), PTCH1 (7.14% vs. 2.7%, P=0.0151), TSHR (5.36% vs. 1.17%, P=0.0253), EIF1AX (3.06% vs. 0%, P=0.02811), JAK2 (2.0% vs. 0.46%, P=0.0311), EP300 (8.67% vs. 4.41%, P=0.0414), PHOX2B (2.20% vs. 0.27%, P=0.0419), SMC1A (3.57% vs. 0%, P=0.0446) and CSF1R (3.02% vs. 1.03%, P=0.0439) had a significantly higher mutation rate in the young-onset primary CRCs. Meanwhile, KRAS was mutated more frequently in late-onset primary CRCs (44.0% vs. 51.3%, P=0.03679). For metastatic CRCs, NTRK1 was found mutated in 12 (3.80%) out of 316 later-onset metastatic CRCs but none out of 129 young-onset metastatic CRCs (P=0.0223). Meanwhile, CIC was mutated in only 1 out of 103 young-onset metastatic CRCs but 17 (6.44%) out of 264 late-onset metastatic CRCs (P=0.0302) and TP53 had a nearly 8% higher mutation rate in young-onset metastatic CRCs (79.01% vs. 71.19%, P=0.0488). Conclusions: Mutation rates were found significantly higher in many genes among young-onset primary CRCs compared to late-onset primary CRCs.

Citation Format: Jingqin Luo, Marios Giannakis, Graham Colditz, Jean Wang, William Chapman, Adetunji T. Toriola, Yoshiko Mito, Reiko Nishihara, Jonathan Nowak, Charles Fuchs, Edward Giovannucci, Andrew T. Chan, Adam Bass, Shuji Ogino, Ryan Fields, Yin Cao. Comparative genomic analysis of young-onset and late-onset colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1228.

Abstract 229: Genome-wide association study by colorectal carcinoma subtype

Over 50 genetic variants have been associated with colorectal cancer (CRC) risk through genome-wide association studies (GWAS), yet these variants represent only a fraction of the total estimated heritability. CRC is a heterogenous disease with diverse tumor etiology. Assessing genetic risk in molecular subtypes may help to identify novel loci and characterize genetic risk among tumor subtypes. We used microsatellite instability (MSI), an established CRC classifier with etiological and therapeutic relevance, to define CRC subtypes for GWAS analyses. We conducted a case-case analysis to estimate odds ratios (OR) and 95% confidence intervals (CI) for association of genome-wide variants with microsatellite stable (MSS) versus unstable (MSI) carcinomas. We ran an inverse-variance weighted fixed-effects meta-analysis across GWAS in a discovery set of 4,163 population-based CRC cases with harmonized microsatellite instability (MSI) marker and imputed genotype data. For each analysis, we used log-additive logistic regression, adjusting for age, sex, and principal components to account for population substructure. We then followed up with replication of 102 SNPs that reached p-values less than 5x10-6 in 1,698 cases. A total of 845 (20.3%) cancer cases were microsatellite unstable in the discovery population and 174 (10.2%) were unstable in the replication population. No variants reached the genome-wide significance level of 5x10-8 in the discovery set. However, we identified two variants that reached a Bonferroni corrected p-value of 4.0x10-4 in the replication set. This included one variant in MLH1 (Replication: OR=1.74, 95% CI=1.53-1.98, p=1.63x10-5; Discovery+Replication: OR=1.45, 95% CI=1.37-1.54, p=9.76x10-11) and one variant in LOC105377645 (Replication: OR=1.70, 95% CI=1.49-1.94, p=5.13x10-5; Discovery+Replication: OR=1.45, 95% CI=1.37-1.54, p=9.76 x 10-11). The MLH1 gene is a DNA mismatch repair gene implicated in Lynch Syndrome, the hallmark of which is microsatellite instability. This is the first genome-wide scan to identify a common variant in MLH1 that is associated with CRC. This variant (minor allele frequency, MAF = 23% in this all European ancestry population) is located in the 5'-untranslated region of MLH1 and is thought to act as a long-range regulator of DCLK3, a potential tumor driver gene. The second variant, located in LOC105377645 with an MAF of 22%, is in an uncharacterized region of the genome and has not previously been implicated in cancer development. These findings suggest that accounting for molecular heterogeneity is important for discovery and characterization of genetic variants associated with CRC risk. We plan to run polytomous regression analyses, increase our sample size, and further investigate CRC subtypes by CIMP, BRAF mutation, KRAS mutation status.

Citation Format: Tabitha A. Harrison, Yiwen Lu, Chenjie Zeng, Flora Qu, Kristin Anderson, Hermann Brenner, Daniel D. Buchanan, Peter T. Campbell, Andrew T. Chan, Jenny Chang-Claude, Graham G. Giles, Bethany Van Guelpen, Michael Hoffmeister, Mark A. Jenkins, Noralane M. Lindor, Roger L. Milne, Polly A. Newcomb, Reiko Nishihara, Michael O. Woods, Shuji Ogino, John D. Potter, Martha L. Slattery, Wei Sun, Stephen N. Thibodeau, Li Hsu, Ulrike Peters. Genome-wide association study by colorectal carcinoma subtype [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 229.

The competing risks Cox model with auxiliary case covariates under weaker missing-at-random cause of failure

In the analysis of time-to-event data with multiple causes using a competing risks Cox model, often the cause of failure is unknown for some of the cases. The probability of a missing cause is typically assumed to be independent of the cause given the time of the event and covariates measured before the event occurred. In practice, however, the underlying missing-at-random assumption does not necessarily hold. Motivated by colorectal cancer molecular pathological epidemiology analysis, we develop a method to conduct valid analysis when additional auxiliary variables are available for cases only. We consider a weaker missing-at-random assumption, with missing pattern depending on the observed quantities, which include the auxiliary covariates. We use an informative likelihood approach that will yield consistent estimates even when the underlying model for missing cause of failure is misspecified. The superiority of our method over naive methods in finite samples is demonstrated by simulation study results. We illustrate the use of our method in an analysis of colorectal cancer data from the Nurses' Health Study cohort, where, apparently, the traditional missing-at-random assumption fails to hold.

Determining Risk of Colorectal Cancer and Starting Age of Screening Based on Lifestyle, Environmental, and Genetic Factors

BACKGROUND & AIMS

Guidelines for initiating colorectal cancer (CRC) screening are based on family history but do not consider lifestyle, environmental, or genetic risk factors. We developed models to determine risk of CRC, based on lifestyle and environmental factors and genetic variants, and to identify an optimal age to begin screening.

METHODS

We collected data from 9748 CRC cases and 10,590 controls in the Genetics and Epidemiology of Colorectal Cancer Consortium and the Colorectal Transdisciplinary study, from 1992 through 2005. Half of the participants were used to develop the risk determination model and the other half were used to evaluate the discriminatory accuracy (validation set). Models of CRC risk were created based on family history, 19 lifestyle and environmental factors (E-score), and 63 CRC-associated single-nucleotide polymorphisms identified in genome-wide association studies (G-score). We evaluated the discriminatory accuracy of the models by calculating area under the receiver operating characteristic curve values, adjusting for study, age, and endoscopy history for the validation set. We used the models to project the 10-year absolute risk of CRC for a given risk profile and recommend ages to begin screening in comparison to CRC risk for an average individual at 50 years of age, using external population incidence rates for non-Hispanic whites from the Surveillance, Epidemiology, and End Results program registry.

RESULTS

In our models, E-score and G-score each determined risk of CRC with greater accuracy than family history. A model that combined both scores and family history estimated CRC risk with an area under the receiver operating characteristic curve value of 0.63 (95% confidence interval, 0.62-0.64) for men and 0.62 (95% confidence interval, 0.61-0.63) for women; area under the receiver operating characteristic curve values based on only family history ranged from 0.53 to 0.54 and those based only E-score or G-score ranged from 0.59 to 0.60. Although screening is recommended to begin at age 50 years for individuals with no family history of CRC, starting ages calculated based on combined E-score and G-score differed by 12 years for men and 14 for women, for individuals with the highest vs the lowest 10% of risk.

CONCLUSIONS

We used data from 2 large international consortia to develop CRC risk calculation models that included genetic and environmental factors along with family history. These determine risk of CRC and starting ages for screening with greater accuracy than the family history only model, which is based on the current screening guideline. These scoring systems might serve as a first step toward developing individualized CRC prevention strategies.

Integrative analysis of exogenous, endogenous, tumour and immune factors for precision medicine

Immunotherapy strategies targeting immune checkpoints such as the CTLA4 and CD274 (programmed cell death 1 ligand 1, PD-L1)/PDCD1 (programmed cell death 1, PD-1) T-cell coreceptor pathways are revolutionising oncology. The approval of pembrolizumab use for solid tumours with high-level microsatellite instability or mismatch repair deficiency by the US Food and Drug Administration highlights promise of precision immuno-oncology. However, despite evidence indicating influences of exogenous and endogenous factors such as diet, nutrients, alcohol, smoking, obesity, lifestyle, environmental exposures and microbiome on tumour-immune interactions, integrative analyses of those factors and immunity lag behind. Immune cell analyses in the tumour microenvironment have not adequately been integrated into large-scale studies. Addressing this gap, the transdisciplinary field of molecular pathological epidemiology (MPE) offers research frameworks to integrate tumour immunology into population health sciences, and link the exposures and germline genetics (eg, HLA genotypes) to tumour and immune characteristics. Multilevel research using bioinformatics, in vivo pathology and omics (genomics, epigenomics, transcriptomics, proteomics and metabolomics) technologies is possible with use of tissue, peripheral blood circulating cells, cell-free plasma, stool, sputum, urine and other body fluids. This immunology-MPE model can synergise with experimental immunology, microbiology and systems biology. GI neoplasms represent exemplary diseases for the immunology-MPE model, given rich microbiota and immune tissues of intestines, and the well-established carcinogenic role of intestinal inflammation. Proof-of-principle studies on colorectal cancer provided insights into immunomodulating effects of aspirin, vitamin D, inflammatory diets and omega-3 polyunsaturated fatty acids. The integrated immunology-MPE model can contribute to better understanding of environment-tumour-immune interactions, and effective immunoprevention and immunotherapy strategies for precision medicine.

Toxicity and Efficacy of a Novel GADD34-expressing Oncolytic HSV-1 for the Treatment of Experimental Glioblastoma

Purpose: Glioblastoma (GBM) is the most common primary central nervous system cancer in adults. Oncolytic HSV-1 (oHSV) is the first FDA-approved gene therapy approach for the treatment of malignant melanoma. For GBM, oHSVs need to be engineered to replicate within and be toxic to the glial tumor but not to normal brain parenchymal cells. We have thus engineered a novel oHSV to achieve these objectives.Experimental Design: NG34 is an attenuated HSV-1 with deletions in the genes encoding viral ICP6 and ICP34.5. These mutations suppress virus replication in nondividing brain neurons. NG34 expresses the human GADD34 gene under transcriptional control of a cellular Nestin gene promoter/enhancer element, whose expression occurs selectively in GBM. In vitro cytotoxicity assay and survival studies with mouse models were performed to evaluate therapeutic potency of NG34 against glioblastoma. In vivo neurotoxicity evaluation of NG34 was tested by intracerebral inoculation.Results: NG34 replicates in GBM cells in vitro with similar kinetics as those exhibited by an oHSV that is currently in clinical trials (rQNestin34.5). Dose-response cytotoxicity of NG34 in human GBM panels was equivalent to or improved compared with rQNestin34.5. The in vivo efficacy of NG34 against two human orthotopic GBM models in athymic mice was similar to that of rQNestin34.5, whereas intracerebral injection of NG34 in the brains of immunocompetent and athymic mice showed significantly better tolerability. NG34 was also effective in a syngeneic mouse glioblastoma model.Conclusions: A novel oHSV encoding GADD34 is efficacious and relatively nontoxic in mouse models of GBM. Clin Cancer Res; 24(11); 2574-84. ©2018 AACR.