Ere are a number of limitations to this study. Our gene expression analysis was KS-176 limited by the availability of a small number of frozen tumor samples and should be viewed as an exploratory analysis that requires validation in other larger datasets. Recently a multicenter rare cancer genome project to investigate periampullary adenocarcinomas has been initiated and data from this effort will represent a potential validation cohort in the future. The consistent correlations between gene expression, protein expression, histology, and outcome do support our findings. In addition the ability to validate our findings in a large separate cohort of ampullary adenocarcinomas lends support to our gene expression analysis. The classification of the origin of periampullary adenocarcinomas is primarily based upon the clinical and pathological determination of the epicenter of the tumor. This classification can be challenging in large, locally advanced tumors. To minimize misclassification, we relied upon full resection specimen review for each sample and strict criteria in regards to tumor percentage and RNA quality. However, the potential to more precisely classify these tumors lends further support to future efforts, as outlined in this study, to classify the tissue of origin of periampullary cancers based on gene expression profiling. Such an approach may actually better reflect the true tissue of origin and expected natural history for each cancer case. The limited availability of frozen tissue samples and the rarity of non-pancreatic periampullary adenocarcinomas have limited boththe molecular and clinical understanding of these cancers. This study improves our understanding of ampullary adenocarcinomas and distinguishes these cancers from pancreatic adenocarcinomas. Ampullary adenocarcinomas demonstrate both molecular and clinical heterogeneity. Further research into the treatment implications of these findings is needed.Supporting InformationFigure S1 Unsupervised hierarchical clustering of all proteins from the 14 ampullary adenocarcinoma samples. (TIF) Figure S2 Clustering of 12 additional ampullary adenocarcino-ma samples (Ehehalt et al.) using the 234 differentially expressed genes identifies a two sample biliary-like subgroup and a 10 patient intestinal-like subgroup (A). Overall survival for the 11 cases with available outcome data (B). (TIF)Table S1 The 234 differentially expressed genes be-tween intestinal-like and biliary-like ampullary subtypes. (DOCX)Table S2 Title Loaded From File Quantitative protein expression data between intestinal-like and biliary-like ampullary subtypes. (DOCX) Methods S1 Methodology for tissue microarray construction, immunohistochemical analysis, microsatellite instability determination, and DNA mutation analysis. (DOCX)Author ContributionsConceived and designed the experiments: MO HW MD SK BB. Performed the experiments: MO J. Zhang KS BB J. Zhi-Qin HW. Analyzed the data: MO J. Zhang SK MD KS SH RH JA GV BB HW. Contributed reagents/materials/analysis tools: MO MD KS RH PR CP RG. Wrote the paper: MO SK MD JA HW J. Zhang.
Each individual cancer genome contains an ‘archaeological record’ of the tumor’s history, and recent studies have begun to infer the order in which mutations have occurred [1,2]. For example, if a certain class of mutations clusters at a certain time in tumor evolution, this might suggest that these mutations were selected at that stage of evolution or that a particular mutation mechanism was active at that time.Ere are a number of limitations to this study. Our gene expression analysis was limited by the availability of a small number of frozen tumor samples and should be viewed as an exploratory analysis that requires validation in other larger datasets. Recently a multicenter rare cancer genome project to investigate periampullary adenocarcinomas has been initiated and data from this effort will represent a potential validation cohort in the future. The consistent correlations between gene expression, protein expression, histology, and outcome do support our findings. In addition the ability to validate our findings in a large separate cohort of ampullary adenocarcinomas lends support to our gene expression analysis. The classification of the origin of periampullary adenocarcinomas is primarily based upon the clinical and pathological determination of the epicenter of the tumor. This classification can be challenging in large, locally advanced tumors. To minimize misclassification, we relied upon full resection specimen review for each sample and strict criteria in regards to tumor percentage and RNA quality. However, the potential to more precisely classify these tumors lends further support to future efforts, as outlined in this study, to classify the tissue of origin of periampullary cancers based on gene expression profiling. Such an approach may actually better reflect the true tissue of origin and expected natural history for each cancer case. The limited availability of frozen tissue samples and the rarity of non-pancreatic periampullary adenocarcinomas have limited boththe molecular and clinical understanding of these cancers. This study improves our understanding of ampullary adenocarcinomas and distinguishes these cancers from pancreatic adenocarcinomas. Ampullary adenocarcinomas demonstrate both molecular and clinical heterogeneity. Further research into the treatment implications of these findings is needed.Supporting InformationFigure S1 Unsupervised hierarchical clustering of all proteins from the 14 ampullary adenocarcinoma samples. (TIF) Figure S2 Clustering of 12 additional ampullary adenocarcino-ma samples (Ehehalt et al.) using the 234 differentially expressed genes identifies a two sample biliary-like subgroup and a 10 patient intestinal-like subgroup (A). Overall survival for the 11 cases with available outcome data (B). (TIF)Table S1 The 234 differentially expressed genes be-tween intestinal-like and biliary-like ampullary subtypes. (DOCX)Table S2 Quantitative protein expression data between intestinal-like and biliary-like ampullary subtypes. (DOCX) Methods S1 Methodology for tissue microarray construction, immunohistochemical analysis, microsatellite instability determination, and DNA mutation analysis. (DOCX)Author ContributionsConceived and designed the experiments: MO HW MD SK BB. Performed the experiments: MO J. Zhang KS BB J. Zhi-Qin HW. Analyzed the data: MO J. Zhang SK MD KS SH RH JA GV BB HW. Contributed reagents/materials/analysis tools: MO MD KS RH PR CP RG. Wrote the paper: MO SK MD JA HW J. Zhang.
Each individual cancer genome contains an ‘archaeological record’ of the tumor’s history, and recent studies have begun to infer the order in which mutations have occurred [1,2]. For example, if a certain class of mutations clusters at a certain time in tumor evolution, this might suggest that these mutations were selected at that stage of evolution or that a particular mutation mechanism was active at that time.
