Abstract P1-07-16: Multi-level gene expression signatures provide significant prognostic information in metastatic breast cancer patients

Background: We have previously demonstrated how transcriptional pathway activity and the molecular subtypes of breast cancer metastases significantly influence patient post-relapse survival. Here we extend our analysis to determine whether the prognostic information provided by gene expression signatures in primary breast tumours is also relevant in the metastatic setting. Specifically, we test the research versions of the Genomic Grade Index (GGI), Mammaprint, Recurrence score (RS) and PAM50 gene signatures along with our own cell-cycle based classifier (CCS).

Methods: 287 patients with morphologically confirmed loco-regional or distant breast cancer relapse were enrolled in the Swedish multicenter TEX trial from December 2002 until June 2007. Of these, sufficient tumour RNA for gene expression profiling was obtained from metastatic tissue by fine needle aspiration from 111 patients (totalling 120 relapse biopsies). Gene signatures were applied as described in the original research articles and their relationship to short (1.5 year) and long-term (5 year) post-relapse survival was assessed using likelihood ratio, Kaplan-Meier and Cox regression analysis.

Results: As anticipated from an aggressive metastatic cohort, the majority of samples (> 70%) were classified into intermediate or high risk groups by all signatures. In both short and long-term survival analysis only PAM50 provided statistically significant prognostic information (short: LRχ2 = 14.7, p = 0.005 and long: LRχ2 = 13.2, p = 0.010), with the cell cycle score signature displaying a prognostic trend in long-term survival only (LRχ2 = 5.2, p = 0.074). Kaplan-Meier curves and Cox regression analysis suggest that the strength of both signatures resides in their ability to select a group of low-risk patients with better long-term survival.

Conclusions: Our findings demonstrate the prognostic utility of the multi-level PAM50 and to a lesser extent, cell cycle score signatures in predicting survival of patients with metastatic breast cancer. Simpler binary gene expression signatures (GGI and Mammaprint) do not appear to capture the same prognostic information and as such may have limited utility in a metastatic setting.

Short and long term survival Likehood Ratios for five gene expression signatures in metastatic breast cancer Short term survival (1.5 year)Long term survival (5 year)Gene SignatureLRχ2P-valueLRχ2P-valueGGI1.30.2510.50.500Mammaprint1.70.1900.60.427RS3.90.1434.40.110CCS2.80.2425.20.074PAM5014.70.00513.20.010GGI: Genomic grade index; RS: Recurrence score; CCS: Cell cycle score

Citation Format: Tobin NP, Lundberg A, Lindström LS, Harrell JC, Egyhazi Brage S, Frostvik Stolt M, Einbeigi Z, Loman N, Malmberg M, Perou CM, Bergh J, Hatschek T. Multi-level gene expression signatures provide significant prognostic information in metastatic breast cancer patients [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 P1-07-16.

Abstract P3-06-08: HDAC6 deacetylates HMGN2 to regulate Stat5a activity and breast cancer growth

Stat5 is a transcription factor utilized by several cytokine/hormone receptor signaling pathways that promotes transcription of genes associated with proliferation, differentiation, and survival of cancer cells. However, there are currently no clinically approved therapies that target Stat5, despite ample evidence that it contributes to breast cancer pathogenesis. Previous research in our lab has shown that the high mobility group nucleosome binding domain 2 (HGMN2) protein serves as a Stat5 co-activator. The activity of HMGN2 has been previously shown to be regulated by acetylation. Here, we show that deacetylation of HMGN2 on lysine residue K2 by histone deacetylase 6 (HDAC6) promotes Stat5-mediated transcription and breast cancer growth. Conversely, in vitro HDAC6 inhibition by pharmacologic and knock-down approaches enhanced HMGN2 acetylation with a concomitant reduction of in vitro Stat5-mediated signaling and global gene expression, and breast cancer growth. In vitro and in vivo treatment of traditional and patient-derived xenograft models with HDAC6 inhibitors resulted in a highly significant reduction of tumor growth. Translationally, it was also found that high levels of acetylated K2 were present in normal human breast tissue, which was lost in primary breast cancers and lymph node metastases. This suggests that blockade of HMGN2 deacetylation as described above is a novel treatment for breast cancer, given that existing HDAC6 inhibitors have a favorable toxicity profile in Phase I trials of other tumor types. Altogether, these results reveal a novel mechanism through which HDAC6 regulates the transcription of Stat5 target genes and demonstrates the utility of HDAC6 inhibition as a potential breast cancer therapeutic.

Citation Format: Clevenger CV, Craig JM, Fiorillo AA, Feeney YB, Harrell JC, Medler TR. HDAC6 deacetylates HMGN2 to regulate Stat5a activity and breast cancer growth [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 P3-06-08.

Molecular subtype and tumor characteristics of breast cancer metastases as assessed by gene expression significantly influence patient post-relapse survival

BACKGROUND

We and others have recently shown that tumor characteristics are altered throughout tumor progression. These findings emphasize the need for re-examination of tumor characteristics at relapse and have led to recommendations from ESMO and the Swedish Breast Cancer group. Here, we aim to determine whether tumor characteristics and molecular subtypes in breast cancer metastases confer clinically relevant prognostic information for patients.

PATIENTS AND METHODS

The translational aspect of the Swedish multicenter randomized trial called TEX included 111 patients with at least one biopsy from a morphologically confirmed locoregional or distant breast cancer metastasis diagnosed from December 2002 until June 2007. All patients had detailed clinical information, complete follow-up, and metastasis gene expression information (Affymetrix array GPL10379). We assessed the previously published gene expression modules describing biological processes [proliferation, apoptosis, human epidermal receptor 2 (HER2) and estrogen (ER) signaling, tumor invasion, immune response, and angiogenesis] and pathways (Ras, MAPK, PTEN, AKT-MTOR, PI3KCA, IGF1, Src, Myc, E2F3, and β-catenin) and the intrinsic subtypes (PAM50). Furthermore, by contrasting genes expressed in the metastases in relation to survival, we derived a poor metastasis survival signature.

RESULTS

A significant reduction in post-relapse breast cancer-specific survival was associated with low-ER receptor signaling and apoptosis gene module scores, and high AKT-MTOR, Ras, and β-catenin module scores. Similarly, intrinsic subtyping of the metastases provided statistically significant post-relapse survival information with the worst survival outcome in the basal-like [hazard ratio (HR) 3.7; 95% confidence interval (CI) 1.3-10.9] and HER2-enriched (HR 4.4; 95% CI 1.5-12.8) subtypes compared with the luminal A subtype. Overall, 25% of the metastases were basal-like, 32% HER2-enriched, 10% luminal A, 28% luminal B, and 5% normal-like.

CONCLUSIONS

We show that tumor characteristics and molecular subtypes of breast cancer metastases significantly influence post-relapse patient survival, emphasizing that molecular investigations at relapse provide prognostic and clinically relevant information. CLINICALTRIALS.GOV: This is the translational part of the Swedish multicenter and randomized trial TEX, clinicaltrials.gov identifier nct01433614 (http://www.clinicaltrials.gov/ct2/show/nct01433614).

Reproducibility of beam alignment using different bite-wing radiographic techniques

Longitudinal radiographic assessment of crestal alveolar bone plays an important role in the diagnosis and long-term evaluation of periodontal disease in patients. Because practitioners use several radiographic techniques to obtain bite-wing radiographs, horizontal and vertical alignment errors could adversely affect the diagnostic impression gained from this type of radiographic examination. The objective of this study was to determine the alignment reproducibility of three different clinical techniques used to acquire bite-wing radiographs. Patients who require bite-wing radiographs as part of a dental school screening process were radiographed with modified standard bite-wing tabs and two different intraoral positioning devices. Horizontal and vertical angular deviations were measured and alignment errors were calculated for each radiograph. The mean total angular alignment error for the standard bite-wing tab technique was 6.2 degrees, whereas the mean alignment error for both positioning devices was less than 1.8 degrees. The results of this study suggest that an intraoral positioning device for acquiring bite-wing radiographs should be used.

Prostaglandin E2 regulates gingival mononuclear cell immunoglobulin production

Histological studies have revealed elevated levels of T and B lymphocytes in inflamed gingival tissue. Functional analysis of these B cells has determined that they are spontaneously secreting large amounts of immunoglobulin. Several components of bacterial plaque which accumulate during the onset of periodontal disease induce polyclonal B cell activation, and are most likely responsible for the "hyperactive" state of these gingival B lymphocytes. In addition to this exaggerated humoral response, increased levels of inflammatory mediators, such as prostaglandin (PG) E2, have been implicated in the pathogenesis of disease. Therefore, the purpose of this study was to determine if PGE2 could regulate immunoglobulin production within inflamed gingival tissue. Specimens were harvested during routine surgery of patients with chronic adult periodontitis. Utilizing an ELISA, elevated levels of IgG were detected in the supernatant of cultured gingival mononuclear cells. Inclusion of indomethacin, which inhibits arachidonic acid metabolites such as PGE2, caused a decrease in IgG levels. PGE2 exerted a biphasic effect upon IgG production, with high doses diminishing and low doses increasing IgG levels. From a clinical perspective, these results suggest that elevated levels of PGE2 associated with inflammation will attenuate an IgG response and, as PGE2 production wanes, the local humoral response will rebound. Interestingly, the combination of low dose PGE2 and IL-4 induced a synergistic rise in IgG production. These findings support the theory that local PGE2 levels can regulate immunoglobulin production and potentiate cytokine induced class switching within gingival tissue.