A pan-sarcoma landscape of telomeric content shows that alterations in RAD51B and GID4 are associated with higher telomeric content

Tumor cells need to activate a telomere maintenance mechanism, enabling limitless replication. The bulk of evidence supports that sarcomas predominantly use alternative lengthening of telomeres (ALT) mechanism, commonly associated with alterations in ATRX and DAXX. In our dataset, only 12.3% of sarcomas harbored alterations in these genes. Thus, we checked for the presence of other genomic determinants of high telomeric content in sarcomas. Our dataset consisted of 13555 sarcoma samples, sequenced as a part of routine clinical care on the FoundationOne®Heme platform. We observed a median telomeric content of 622.3 telomeric reads per GC-matched million reads (TRPM) across all samples. In agreement with previous studies, telomeric content was significantly higher in ATRX altered and POT1 altered sarcomas. We further observed that sarcomas with alterations in RAD51B or GID4 were enriched in samples with high telomeric content, specifically within uterus leiomyosarcoma for RAD51B and soft tissue sarcoma (not otherwise specified, nos) for GID4, Furthermore, RAD51B and POT1 alterations were mutually exclusive with ATRX and DAXX alterations, suggestive of functional redundancy. Our results propose a role played by RAD51B and GID4 in telomere elongation in sarcomas and open research opportunities for agents aimed at targeting this critical pathway in tumorigenesis.

A Novel HRD Signature Is Predictive of FOLFIRINOX Benefit in Metastatic Pancreatic Cancer

BACKGROUND

Pancreatic cancer (PC) represents an aggressive disease with median overall survival (OS) of less than 1 year in the front-line setting. FOLFIRINOX and gemcitabine and paclitaxel (GP) are standard of care options for these patients; however, optimal selection of therapy is challenging.

METHODS

Comprehensive genomic profiling was performed on 8358 PC patients. Outcomes were available for 1149 metastatic PC patients treated with 1L FOLFIRINOX or GP. A scar-based measure of HRD was called using a machine learning-based algorithm incorporating copy number and indel features.

RESULTS

A scar-based HRD signature (HRDsig) was identified in 9% of patients. HRDsig significantly co-occurred with biallelic alterations in BRCA1/2, PALB2, BARD1, and RAD51C/D, but encompassed a larger population than that defined by BRCA1/BRCA2/PALB2 (9% vs. 6%). HRDsig was predictive of 1L FOLFIRNOX chemotherapy benefit with doubled OS relative to gemcitabine and paclitaxel (GP) (rwOS aHR 0.37 [0.22-0.62]), including 25% of the population with long-term (2 year+) survival in a real-world cohort of patients. Less benefit from FOLFIRINOX was observed in the HRDsig(-) population. Predictive value was seen in both the BRCA1/2/PALB2 mutant and wildtype populations, suggesting additional value to mutational profiling.

CONCLUSION

A scar-based HRD biomarker was identified in a significant fraction of PC patients and is predictive of FOLFIRINOX benefit. Incorporating a biomarker like HRDsig could identify the right patients for platinum chemotherapy and potentially reduce FOLFIRINOX use by over 40%, minimizing toxicities with similar survival outcomes. Confirmatory studies should be performed.

Abstract 1243: Identification of aneuploidy biomarkers associated with response to first-line treatment of metastatic pancreatic cancer

Background: NCCN guidelines for first-line treatment of patients with metastatic pancreatic cancer includes either FOLFIRINOX or gemcitabine plus paclitaxel; however, these two treatment regimens have not been compared in a randomized clinical trial. In this study, we investigated genomic predictors of treatment response to guide this treatment decision.

Methods: We selected 1,250 patients with metastatic pancreatic cancer who were treated with first-line FOLFIRINOX (FOLF, n = 588) or gemcitabine plus paclitaxel (G+P, n = 662) within the nationwide de-identified Flatiron Health-Foundation Medicine clinico-genomic database (CGDB). The de-identified data originated from approximately 280 US cancer clinics (~800 sites of care). Comprehensive genomic profiling was performed by Foundation Medicine on tumor samples from each patient as part of the standard of care. Gain/loss status as well as loss of heterozygosity (LOH) status of each chromosome arm was assessed using a custom research-use only algorithm that utilizes copy number model calls for each segment and SNP MAF information from sequencing data. Univariable Cox proportional hazards regression was used to identify chromosome arm-level aneuploidies associated with survival in patients treated with first-line FOLF or G+P. In each treatment cohort, a multivariable Cox model was built using the bidirectional stepwise regression procedure to select aneuploidy features associated with survival. A binary risk score was calculated based on the linear predictor of the multivariable Cox model and categorized as high vs low using a median threshold.

Results: Among the FOLF-treated cohort, we identified six aneuploidy features associated with survival (Bonferroni adjusted p < 0.05). FOLF-treated patients with a low FOLF risk score had better survival compared to those with a high FOLF risk score (HR: 0.46, 95%CI: 0.34-0.61, p = <0.001). This association was not observed among G+P-treated patients (HR: 0.86, 95%CI: 0.66-1.11, p = 0.25). Among the G+P treated cohort; eight aneuploidy features were associated with survival (Bonferroni adjusted p < 0.05). G+P-treated patients with a low G+P risk score had better survival compared to patients with a high G+P risk score (HR: 0.43, 95%CI: 0.33-0.57, p = <0.001). This association was not observed among FOLF-treated patients (HR: 0.86, 95%CI: 0.66-1.12, p = 0.25). These findings remained after adjusting for clinical features including surgery and ECOG performance status (HRG+P: 0.52, p = <0.001; HRFOLF: 0.5, p = <0.001).

Conclusions: In metastatic pancreatic cancer, we found different chromosome arm-level aneuploidies were associated with survival for FOLF and G+P regimens which suggests an aneuploidy-based risk score may have utility in choosing first-line treatment.

Citation Format: Kuei-Ting Chen, Radwa Sharaf, Garrett Frampton, Lee Albacker, Ericka Ebot. Identification of aneuploidy biomarkers associated with response to first-line treatment of metastatic pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1243.

Abstract 1574: Circadian clock gene expression and lethal prostate cancer outcomes

Background: Converging evidence points to a potential role of disruption of the circadian rhythm in prostate cancer progression. There is limited human data in prostate tissue examining the biological consequences of alterations in genes involved in circadian rhythm on outcomes among prostate cancer patients.

Methods: To test the hypothesis that tissue expression of circadian-related genes was associated with prostate cancer outcomes, we leveraged data from the Physicians' Health Study (PHS) and the Health Professionals Follow-Up Study (HPFS) prostate tumor cohorts. Whole transcriptome expression profiling was performed on 404 prostate cancer cases, including 113 lethal cases (metastatic disease or prostate cancer death) and 291 indolent cases (>8 years from diagnosis without evidence of metastasis). Using logistic regression models, we assessed whether mRNA expression levels in tumor (N=404) or paired normal prostate tissue (N=202) of eleven circadian-related genes (AANAT, CLOCK, CRY1, CRY2, CSNK1E, MTNR1B, NPAS2, OPN4, PER1, PER2, PER3) were associated with lethal prostate cancer, stage (T2 vs. T3+), Gleason grade at diagnosis (<8 vs. ≥8), and biomarkers of angiogenesis and apoptosis. We calculated odds ratios and 95% confidence intervals (95% CIs) per standard deviation increase in gene expression.

Results: Pathway analyses showed a statistically significant association between the eleven circadian genes and lethal disease (global test p-value = 5.1e-05). On an individual gene level, men with higher tumor expression of Period Circadian Regulator 1 (PER1) gene had a reduced risk of lethal disease, independent of grade and stage (OR: 0.75, 95% CI: 0.59-0.97). High tumor expression of PER1 (OR: 0.72, 95% CI: 0.57-0.91) and Cryptochrome Circadian Regulator 2 (CRY2) (OR: 0.79, 95% CI: 0.63-1.00) were associated with lower Gleason grade tumors. High tumor expression of PER1 was associated with lower levels of cell proliferation and lower levels of angiogenesis markers; Neuronal PAS Domain Protein 2 (NPAS2) was associated with markers of apoptosis. For none of the genes was expression in normal prostate tissue associated with lethal prostate cancer (global test p-value = 0.06).

Discussion: We found higher expression of several of the circadian related genes were associated with less aggressive prostate cancer features. In line with these findings, PER1 has been suggested to be a tumor suppressor in previous studies. This supports the idea that maintenance of circadian clock function may protect tumor progression.

Citation Format: Sarah C. Markt, Ericka Ebot, Iona Cheng, Lynne Wilkens, Ayesha Shafi, Karen Knudsen, Kathryn Penney, Lorelei Mucci, Travis Gerke. Circadian clock gene expression and lethal prostate cancer outcomes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1574.

Abstract A045: All happy families are alike: Transcriptomic homogeneity in indolent prostate tumors is a useful prognostic biomarker

Purpose: To derive a gene expression score of transcriptomic homogeneity in localized prostate tumor specimens, and assess its prognostic utility for metastatic or lethal disease.

Background: At the time of prostate cancer diagnosis, improved biomarkers are needed to distinguish tumors with metastatic potential versus those likely to follow an indolent course. Previous evidence suggests that gene expression aberrations are homogeneous in nonaggressive tumors, while transcriptomic profiles are disregulated in widely varying patterns across metastasis-prone tumors. Here, we investigate whether a measure of transcriptomic homogeneity has prognostic utility.

Study Population: Gene expression profiles of noncancerous prostate tissue from the Genotype-Tissue Expression (GTEx) project (n = 106) were used to develop the homogeneity measure. Prognostic utility of the score was assessed in a study nested in the Health Professionals Follow-up Study (HPFS) and Physicians’ Health Study (PHS), in which whole-transcriptome gene expression was quantified from archival surgical tumor tissue. Cases (n = 113) were men who died of prostate cancer or developed metastatic disease, and controls (n = 291) had at least 8 years of metastasis-free survival. Men were diagnosed with prostate cancer between 1982 and 2005, and median follow-up time was 14.0 years. TCGA data (n = 333) were further used to investigate associations of the expression score with Gleason.

Methods: RNA-seq profiles from GTEx were filtered to retain genes persistently expressed across noncancerous prostate tissue specimens. Remaining genes were placed into decile bins on the basis of median expression across samples. The 25 lowest variance genes within each bin were selected to generate a 250-gene panel. Transcriptome homogeneity scores for patients in HPFS and PHS were calculated by summing the standard deviations over the decile bins, where standard deviations were calculated using patient-specific data across 25 genes in each bin. Associations between the score and lethal disease were assessed through logistic regression and AUC analyses. Associations between the homogeneity score and Gleason score in TCGA samples were evaluated via Pearson correlations.

Results: High transcriptomic heterogeneity was strongly associated with lethal or metastatic outcomes. A crude odds ratio of 3.36 (95% CI 2.12-5.41; p<0.001) was estimated for patients with above median heterogeneity scores compared to those with homogenous expression (those with less than or equal to median heterogeneity). This association persisted with adjustment for Gleason (<7, 3+4, 4+3, 8, 9-10) with an odds ratio of 2.04 (95% CI 1.19-3.51; p=0.01). Addition of heterogeneity scores to Gleason improved the AUC of the Gleason-only model from 0.82 (95% CI 0.77-0.86) to 0.84 (95% CI 0.80-0.88; p=0.01 for improvement). Higher heterogeneity also tracked with higher Gleason score in TCGA with a correlation of 0.33 (95% CI 0.23-0.42; p<0.001).

Conclusions: Transcriptomic homogeneity, as measured by variation across gene sets that are typically stable in normal prostate tissue, is able to distinguish indolent from lethal prostate cancers. Further investigation and discovery of gene sets using this novel approach is likely to deliver new biologic insights and clinically actionable biomarker sets.

Citation Format: Travis Gerke, Svitlana Tyekucheva, Jordan H. Creed, Kathryn L. Penney, Jennifer A. Sinnott, Ericka Ebot, Anders E. Berglund, Massimo Loda, Meir J. Stampfer, Peter Kraft, Giovanni Parmigiani, Lorelei A. Mucci. All happy families are alike: Transcriptomic homogeneity in indolent prostate tumors is a useful prognostic biomarker [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr A045.

Abstract 2498: Amine and lipid metabolites are enriched in advanced prostate cancer

Background: Obesity is an established risk factor for advanced prostate cancer. We performed whole body metabolomics profiling in pre-diagnostic blood specimens to identify metabolites associated with risk of advanced prostate cancer, and assess the extent to which obesity modifies this association.

Methods: Our study was nested within the prospective US Health Professionals Follow-up Study during the study period 1993 and 2014. We selected 212 advanced prostate cancer (≥ stage T3b, distant metastasis or cancer death during follow-up) patients and 212 matched controls for whom pre-diagnostic bloods were collected with a median 5.5 years prior to diagnosis. Metabolomics profiling was performed at the Broad Institute using liquid chromatography-tandem mass spectrometry to assay 295 known metabolites. We estimated odds ratios and 95% confidence intervals using multivariable conditional logistic regression to examine associations of individual metabolites and cancer risk. We also performed pathway analyses using a method adapted from gene set enrichment analysis to identify metabolite classes associated with advanced prostate cancer.

Results: We identified 29 circulating metabolites in pre-diagnostic bloods that were significantly associated with advanced prostate cancer risk. These metabolites included carnitines and phospholipids, diacylglycerols (DAG) and triacylglycerols (TAG). Using pathway analyses, we found metabolites in DAG and TAG pathways were highly significantly (FDR<10-8) enriched in men with advanced prostate cancer. 166 of the 295 metabolites were significantly (p<0.001) associated with obesity. When we stratified by a man’s obesity status, we observed unique metabolomics profiles associated with advanced prostate cancer. Circulating amines (including carnitines) were associated with advanced prostate cancer in overweight men while lipid metabolites (including DAGs and TAGs) were associated with advanced cancer in the healthy weight men.

Conclusion: Altered levels of TAG and DAG metabolites in prediagnostic bloods are strongly associated with an increased risk of advanced prostate cancer, independent of obesity. The finding that circulating lipids were specifically associated with advanced prostate cancer in healthy weight patients suggests there are men with normal body mass index but who are metabolically obese. The specific lipid metabolite classes enriched in advanced prostate cancer support the hypothesis that obesity acts through dysregulation of liver fatty acid metabolism rather than through metabolic actions of the adipose tissue itself.

Citation Format: Lorelei A. Mucci, Ericka Ebot, Clary Clish, Sarah Markt, Renea Taylor, Matthew Watt, Philip Kantoff, Edward Giovanucci, Matthew VAnder Heiden, Kathryn Wilson. Amine and lipid metabolites are enriched in advanced prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2498. doi:10.1158/1538-7445.AM2017-2498

Abstract 4236: Gene expression profiling of prostate tissue identifies biological pathways associated with TMPRSS2:ERG gene fusion

Background: TMPRSS2:ERG, a hormonally regulated gene fusion present in about half of prostate tumors, is the most common somatic event in prostate cancer. There is intriguing evidence to suggest that TMPRSS2:ERG-positive tumors may define a distinct subgroup of prostate cancer. In this study we compared gene expression profiles according to fusion status to identify genes and biological pathways differential expressed by TMPRSS2:ERG.

Methods: The study included men with prostate cancer in the Health Professionals Follow-up Study and the Physicians’ Health Study diagnosed between 1982 and 2004 and followed through 2012. Tumor biomarker data was available for archival tumor tissue from 380 cases, 191 of whom also had gene expression data for adjacent normal tissue. Whole genome mRNA expression profiling (20,254 genes) was performed using the Affymetrix 1.0 ST array. TMPRSS2:ERG tumor status was assessed by a genetically validated IHC assay for ERG. To relate expression of individual genes to ERG we used linear regression. Gene Set Enrichment Analysis (GSEA) was used to identify pathways of genes associated with ERG in both tumor and adjacent normal tissue. Data from The Cancer Genome Atlas (TCGA) was used to validate these findings.

Results: Among 380 cases, 186 (49%) of tumors were positive for the gene fusion.

Genome-wide differential expression analysis identified 492 genes upregulated and 369 genes downregulated in tumor tissue comparing ERG+ to ERG- tumors (FDR p-value < 0.05). No genes were identified in the adjacent normal tissue at this significance level. 772 of the 861 genes (90%) identified in the HPFS/PHS dataset were confirmed in TCGA (448 upregulated and 324 downregulated). The top ten genes included ERG, WNK2, CACNA1D, HES1, SEPT9, PLA2G7, TDRD1, ANTXR2, SORBS2, and MYO6. Enrichment analysis identified a number of metabolic pathways associated with ERG tumor status including pathways involved in amino acid and fatty acid metabolism.

Conclusions: We identified significant differences in gene expression profiles in prostate tumor tissue according to TMPRSS2:ERG status, providing supportive evidence of this fusion as a unique subtype.

Citation Format: Ericka Ebot, Masis Isikbay, Travis Gerke, Thomas U. Ahearn, Rachel S. Kelly, Svitlana Tyekucheva, Andreas Pettersson, Kathryn L. Penney, Lorelei A. Mucci. Gene expression profiling of prostate tissue identifies biological pathways associated with TMPRSS2:ERG gene fusion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4236. doi:10.1158/1538-7445.AM2017-4236

Differential gene expression in prostate tissue according to vasectomy

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Background: We previously found that vasectomy was associated with an increased risk of prostate cancer, and particularly, risk of lethal prostate cancer in the Health Professionals Follow-up Study (HPFS). However, the possible biological basis for this finding is unclear. In this study, we explored possible biological mechanisms by assessing differences in gene expression in the prostate tissue of men with and without a history of vasectomy prostate cancer diagnosis. Methods: Within the HPFS, vasectomy data and gene expression data (20,254 genes) was available from archival tumor tissue from 263 cases, 124 of whom also had data for adjacent normal tissue. To relate expression of individual genes to vasectomy we used linear regression adjusting for age and year at diagnosis. We ran gene set enrichment analysis to identify pathways of genes associated with vasectomy. Results: Among 263 cases, 67 (25%) reported a vasectomy prior to cancer diagnosis. Mean age at diagnosis was 66 years among men without and 65 years among men with vasectomy. Median time between vasectomy and prostate cancer diagnosis was 25 years. Gene expression in tumor tissue was not associated with vasectomy status. In adjacent normal tissue, three individual genes were associated with vasectomy with Bonferroni-corrected p-values of < 0.10: RAPGEF6, OR4C3, and SLC35F4. Gene set enrichment analysis found five pathways upregulated and seven pathways downregulated in men with vasectomy compared to those without in normal prostate tissue with a FDR < 0.05. Upregulated pathways included several immune-related gene sets and G-protein-coupled receptor gene sets. Conclusions: We identified significant differences in gene expression profiles in normal prostate tissue according to vasectomy status among men treated for prostate cancer. The fact that such differences existed several decades after vasectomy provides support for the idea that vasectomy may play a role in the etiology of prostate cancer.