Kosiorek, HE

Abstract Introduction: Homologous recombination (HR) is essential for repairing double-stranded DNA breaks. Tumors deficient in DNA HR display high levels of copy number aberrations including amplifications, deletions, and breakpoints. Studies in BRCAmut cancers have shown that HR deficiency (HRD) renders triple negative breast carcinoma (TNBC) sensitive to carboplatin or Poly(ADP-ribose) polymerase (PARP) inhibitors via a synthetic lethal interaction, as previously described. Clinical observations in breast and other solid tumors suggest that the HRD phenotype may arise independently of BRCA1/2 mutation. The implications of HRD enrichment in PD-L1, PD-L2, Jak2 (PDJ) 9p24.1 amplified TNBC are not known. Our goal was to determine the HRD status in PDJ enriched tumors, and the potential association of the PDJ amplicon with a BRCA like HRD phenotype. Methods: Archival fresh frozen and formalin-fixed paraffin embedded (FFPE) tumor samples from 41 patients with TNBC were obtained from 1998-2015. Tumor populations (diploid, tetraploid, and aneuploidy) were sorted using DNA content flow cytometry and interrogated with oligonucleotide array comparative genomic hybridization (aCGH). Tumor homologous recombination deficiency (HRD) scores were calculated by number of interstitial aberrations (IA) in their genomes (HRD-IA). A cut-off of < 40 (low), > 40 (high) or > 50 (very high) was assigned based on our studies of known BRCAmut tumors. Data were compared between HRD groups using chi-square, ANOVA F-test or log-rank test. Results: 14/41 (34%) TNBC patients had high HRD-IA score and 6/41 (14.6%) had very high HRD-IA score. The median age was 61.8 years (SD = 12.8), the average tumor size was 3.1cm (SD = 2.6), 42% were node positive, 24% were pre-menopausal, 19% were Black, Hispanic, or Asian/Pacific Islander. Genetic testing was negative for BRCA1/2 mutations in 9/41 patients, including 3 high and very high HRD-IA score patients. There was no difference in the OS at 5-years [74% versus 59% (p = 0.907)] in the high HRD-AI group. 12/41 (29%) patients were PDJ+. In the PDJ+ patients, 4/12 (33.3%) had HRD > 40 and 1/12 (8.3%) had HRD > 50 compared to the PDJ- patients where 10/29 (34%) had high HRD-IA score and 5/29 (17%) had a very high HRD-IA score, p=0.463. Patients with inflammatory TNBC were significantly more likely to have high HRD-IA score 4/6 (66%) compared to non-inflammatory TNBC 8/31 (26%), p=0.05. Conclusions: We describe a unique group of TNBC patients with similar patient characteristics, tumor size, nodal status, and stage when compared by low, high and very high HRD-IA score. For inflammatory TNBC, there was statistically significant percentage of patients with a high HRD-IA score. We did not see a statistically significant correlation with 9p24.1 amplification based on HRD-IA score which has been suggested in other data sets. The HRD-IA score did not statistically impact OS but there was a suggestion that those with a higher score may have an improved OS potentially due to chemotherapy sensitivity. Further study with a greater number of patients to adequately power the study is needed to determine whether our initial findings can be confirmed and whether the HRD-IA score can be used to define a specific subset of TNBC patients. Citation Format: Gawryletz CD, Anderson KS, Northfelt DW, Kosiorek HE, Linnaus ME, Ocal IT, McCullough AE, Pockaj BA, Barrett MT. Homologous recombination deficiency in PD-L1, PD-L2, Jak2 (PDJ) amplified triple negative breast carcinoma [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-05-19.

Abstract Introduction: We have previously identified a 9p24.1 amplicon targeting PD-L1/JAK2 (PDJ) in subset (26.7%) of triple negative breast cancer (TNBC) patients. The PDJ amplicon is common in newly diagnosed and chemotherapy treated TNBCs and is associated with a worse prognosis. Our goal in this study was to determine whether immunohistochemistry (IHC) evaluation could identify those patients who harbor the PDJ amplicon. Methods: TNBC patients from 1999 to 2015 whose tumors were flow-sorted and evaluated by array-based comparative genomic hybridization (CGH) were identified; paraffin slides were obtained for IHC staining evaluation of JAK-2, phosphorylated STAT3 (pSTAT3), and PD-L1. Pathologic analysis consisted of scoring the stains for intensity (0-3+) and the relative percent of tumor cells with positive staining; positive score was defined as 3+ for any percent staining. Statistical analysis of IHC staining was performed to determine association with the PDJ amplicon defined by focal 9p24.1 copy number gain with CGH log2ratios of >1.0 for each sorted TNBC sample. Results: Eleven of 43 TNBC patients evaluable by IHC had the PDJ amplicon. There was no association between PDJ amplification and IHC staining for JAK-2, pSTAT3, or PD-L1 regardless of staining intensity or percentage tumor cells positive. Table 1 describes PDJ amplicon status and positivity for JAK2, pSTAT3 and PD-L1. Of PDJ-positive samples, 64%, stained positive for JAK2, 27% positive for pSTAT3, but 0% for PD-L1 in tumor cells. However, in the PDJ-negative group, 69% still stained positive for JAK2, 19% positive for pSTAT3, and 9% for PD-L1. Table 1: PDJ amplicon status and IHC staining JAK2 (3+) (n;%)pSTAT3 (3+) (n;%)PD-L1 (3+) (n;%)PDJ - (n=32)22;69%6;19%3;9%PDJ + (n=11)7;64%3;27%0;0% JAK2: Most PDJ-positive samples (10/11, 91%) showed some JAK-2 staining. Although one had only 1+ staining at 5% of the cells, the majority (7/11, 64%) had staining of 3+ and >10% of the cells with 2 patients demonstrating 3+ staining of 75% and 90% of the cells. However, those patients without the PDJ amplicon also exhibited JAK2 staining, with 66% (n= 22) of PDJ-negative cases staining strongly for JAK-2 (3+) and > 10% of cells. pSTAT3: All but one PDJ-positive case demonstrated some staining (1+ or greater) for pSTAT3; the staining intensity and percent positivity were much less than the JAK-2 staining with only 2 cases (18%) having 3+ staining of > 10%. Similar staining was seen in the PDJ-negative cohort; 75% of PDJ-negative patients had some pSTAT3 staining (1+ or greater) and 1 patient (5%) exhibited 3+ staining > 10%. PD-L1: Finally, the PD-L1 staining was low overall with only 18% of PDJ-positive cases demonstrating some staining for PD-L1. Notably, only one case stained 3+ with 20% positivity while the majority of the samples had a 2+ intensity encompassing 5-50% of the cells. Conclusions: IHC staining for JAK2, pSTAT3, or PD-L1 was not associated with the presence of the PDJ amplicon. Notably positive IHC staining for JAK2 was observed for both PDJ-positive and PDJ-negative tumor cells, thereby nullifying its application as a screening tool for PDJ amplification. Alternative methods, such as fluorescence in situ hybridization, are needed to identify PDJ-positive patients for further study. Citation Format: Linnaus ME, Kosiorek H, Ocal IT, Dixon L, Barrett MT, Gawryletz CD, Anderson KS, McCullough AE, McEachron TA, Pockaj BA. Immunohistochemistry cannot be used to detect PD-L1/JAK-2 amplification [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-03-13.