Lineage Relationships of Gleason Patterns in Gleason Score 7 Prostate Cancer
John C Cheville, Irina V Kovtun, Steven J Murphy, Sarah H Johnson, Shabnam Zarei, Farhad Kosari, William Sukov, Edgardo J Parilla Castellar, Robert J Karnes, George Vasmatzis. Mayo Clinic, Rochester, MN
Background: The presence of Gleason pattern 3 and 4 (Gleason score 7) portends a significantly more aggressive tumor than Gleason pattern 3 alone (Gleason score 6), and therefore it is critical to understand the genomic relationship of Gleason pattern 3 to 4. We performed next generation DNA sequencing on Gleason score 7 prostate cancer to better define this relationship.
Design: In this study, we utilized laser capture microdissection and whole genome amplification to perform massively parallel mate-pair sequencing from Gleason pattern 3 and adjacent Gleason pattern 4 in 14 Gleason score 7 prostate cancers. Laser capture microdissection was used to separately collect and isolate Gleason patterns, and an DNA amplification process was performed prior to next generation sequencing. The use of the mate-pair sequencing protocol allowed for the identification of large chromosomal alterations within the Gleason patterns, and bioinformatics analysis used a unique binary indexing algorithm to map sequence data to the human genome. In prostate cancer with TMPRSS2-ERG, PCR was performed in both Gleason patterns within the same tumor to identify the specific breakpoints.
Results: Analysis of the landscape of large chromosomal alterations identified 10 to 140 breakpoints per tumor. Recurrent chromosomal translocations were uncommon, and there was genetic heterogeneity with over 1000 unique breakpoints within the set of 14 tumors. The number of breakpoints differed significantly between tumors, and between Gleason patterns within the same tumor. However, common breakpoints were identified between Gleason patterns in the same tumor. Fusion of TMPRSS2 and ERG and loss of PTEN were the most recurrent abnormalities, and were present in eight and four cases, respectively. Hierarchical clustering analysis revealed that Gleason pattern 3 had greater similarity to its partner Gleason pattern 4 than to Gleason pattern 3 from other patients. In cases with TMPRSS2-ERG, Gleason pattern 3 and Gleason pattern 4 shared the identical breakpoints.
Conclusions: Our analysis confirms the genetic heterogeneity of prostate cancer both within the same tumor as well as between different patient's tumors. In addition, we show directly that Gleason pattern 3 and Gleason pattern 4 share chromosomal alterations with identical breakpoints indicating the clonal relationship of Gleason patterns within the same tumor.
Category: Genitourinary (including renal tumors)
Monday, March 4, 2013 1:00 PM
Poster Session II # 151, Monday Afternoon