Abstract P6-05-08: Integrating whole exome sequencing data with RNAseq and quantitative proteomics to better inform clinical treatment decisions in patients with metastatic triple negative breast cancer
Authors: Soon-Shiong P , Rabizadeh S , Benz S , Cecchi F , Hembrough T , Mahen E , Burton K , Song C , Senecal F , Schmechel S , Pritchard C , Dorschner M , Blau S , Blau A 
Published: May 2016

Background: The use of next-generation sequencing has significantly advanced personalized medicine for patients (pts) with breast cancer. Despite this technological advancement, there remains the challenge of understanding how and if tumor heterogeneity can confound molecular analysis and treatment decisions. It has been shown that the expression of ER, PR, and HER2 can vary widely within different areas of the same tumor and between matched primary and metastatic lesions. The "Intensive Trial of OMics in Cancer"-001 (ITOMIC-001; NCT01957514) enrolls pts with metastatic TNBC who are platinum-naive and scheduled to receive cisplatin. Multiple biopsies of up to 7 metastatic sites are performed prior to cisplatin and repeated upon completion of cisplatin and following subsequent therapies. A subset of specimens is chosen for DNA sequencing, RNA sequencing, and quantitative proteomics. We explored the discordance of genomic and proteomic alterations for intrapatient and temporal heterogeneity in pts with TNBC, and the potential benefit of panomic analysis to better inform treatment decisions.

Methods: Between 7 and 107 tumor samples/biopsy specimens were obtained from each pt from 1-23 different time points. Blood samples were collected for matched tumor-normal genomic analysis. DNA sequencing data were processed using Contraster; RNASeq data confirmed the presence of gene mutations and was used to identify mutational and transcript abundance. PARADIGM was used to determine associations between gene mutations and signaling pathways. Selected reaction monitoring-mass spectrometry (SRM-MS) was used for proteomics analysis.

Results: Almost all pts had loss of TP53 (common in TNBC), and 5 pts had germline BRCA1/2 events, some exhibiting a signature of mutations corresponding to a mismatch repair defect in ≥1 pt. FGFR1/2/3 mutations/amplifications occurred in 5 pts. Three of 12 pts (25%) achieved partial responses after receiving treatments (post cisplatin) based on the molecular profile of their tumor: 1 pt with two FGFR2 activating mutations treated with ponatinib, 1 with a germline BRCA2 mutation treated with veliparib, and 1 with highly expressed Gpnmb treated with an antibody drug conjugate against Gpnmb. Tumor samples showed increased mutational and rearrangement burdens over time but shared mutational characteristics that were unique to each pt. Through the shared alterations across time points for 3 pts, it was possible to reconstruct the clonal history and heterogeneity of the tumors as various therapeutic approaches were attempted.

Conclusions: Here we show in TNBC, intrapatient and temporal heterogeneity that may lead to a lack of response to identified targeted therapies. Tumor samples taken over time from the same pt become enriched for more complex genomic structures post therapy but share mutational characteristics, indicating the presence of recurrent tumor populations. This study enabled us to reconstruct the clonal history and heterogeneity of tumors across space (metastatic vs primary at t=0) and time, illustrating the need for comprehensive molecular analysis and combination/multi-targeted therapeutics for optimal treatment in TNBC.

Citation Format: Soon-Shiong P, Rabizadeh S, Benz S, Cecchi F, Hembrough T, Mahen E, Burton K, Song C, Senecal F, Schmechel S, Pritchard C, Dorschner M, Blau S, Blau A. Integrating whole exome sequencing data with RNAseq and quantitative proteomics to better inform clinical treatment decisions in patients with metastatic triple negative breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-05-08.