Lysine-specific demethylase 1A (KDM1A/LSD1) is a FAD-dependent enzyme that catalyzes the oxidative demethylation of histone H3K4me1/2 and H3K9me1/2 repressing and activating transcription, respectively. Although the active site is expanded compared to that of members of the greater amine oxidase superfamily, it is too sterically restricted to encompass the minimal 21-mer peptide substrate footprint. The remainder of the substrate/product is therefore expected to extend along the surface of KDM1A. We show that full-length histone H3, which lacks any posttranslational modifications, is a tight-binding, competitive inhibitor of KDM1A demethylation activity with a Ki of 18.9 ± 1.2 nM, a value that is approximately 100-fold higher than that of the 21-mer peptide product. The relative H3 affinity is independent of preincubation time, suggesting that H3 rapidly reaches equilibrium with KDM1A. Jump dilution experiments confirmed the increased binding affinity of full-length H3 was at least partially due to a slow off rate (koff) of 1.2 × 10−3 s−1, corresponding to a half-life (t1/2) of 9.63 min, and a residence time (τ) of 13.9 min. Independent affinity capture surface plasmon resonance experiments confirmed the tight-binding nature of the H3/KDM1A interaction, revealing a Kd of 9.02 ± 2.3 nM, a kon of (9.3 ± 1.5) × 104 M−1 s−1, and a koff of (8.4 ± 0.3) × 10−4 s−1. Additionally, no other core histones exhibited inhibition of KDM1A demethylation activity, which is consistent with H3 being the preferred histone substrate of KDM1A versus H2A, H2B, and H4. Together, these data suggest that KDM1A likely contains a histone H3 secondary specificity element on the enzyme surface that contributes significantly to its recognition of substrates and products.

Background Nodal staging with sentinel node biopsy (SLNB), post-lumpectomy radiotherapy (RT), and endocrine therapy (ET) for estrogen receptor-positive (ER+) tumors is valuable in the treatment of early-stage (stages 1 or 2) breast cancer but used less often for elderly women. Methods This retrospective study investigated women referred for surgical evaluation of biopsy-proven primary early-stage invasive breast cancer from January 2001 to December 2010. Clinicopathologic features, treatment course, and outcomes for women ages 80–89 years and 50–59 years were compared. Results The study identified 178 eligible women ages 80–89 years and 169 women ages 50–59 years. The elderly women more often had grade 1 or 2 disease (p = 0.003) and ER+ tumors (p = 0.007) and less frequently had undergone adjuvant therapies (all p ≤ 0.001). Lumpectomy was performed more commonly for the elderly (92 vs. 83 %, p = 0.02), and axillary surgery was less commonly performed (46 vs. 96 %; p < 0.001). Fewer elderly women had undergone post-lumpectomy RT (42 vs. 89 %; p < 0.001) and ET for ER+ tumors (72 vs. 95 %; p < 0.001). During the median follow-up period of 56 months for the 80- to 89-year old group and 98 months for the 50- to 59-year-old group, death from breast cancer was similar (4 vs. 5 %; p = 0.5). The two groups respectively experienced 7 versus 6 locoregional recurrences and 11 versus 13 distant recurrences. Conclusions The octogenarians had disease survivorship similar to that of the younger women despite less frequent use of adjuvant therapies, likely reflecting lower-risk disease features. Whether increased use of axillary surgery, post-lumpectomy RT, and/or ET for ER+ tumors would further improve outcomes is an important area for further study, but treatment should not be deferred solely on the basis of age.

Background Octogenarians with early-stage breast cancer often have low-risk tumor biology. However, optimal treatment strategies for those with high-risk biology remain unclear. Methods We reviewed the records of women ages 80–89 years with biopsy-proven, Stage I–II invasive breast cancer who were referred for surgical evaluation from January 2001 through December 2010. High-risk was defined as human epidermal growth factor receptor-positive (HER2+), triple-negative (TN), or histologic grade 3 disease. Results Among 178 patients, 40 (22%) were high-risk: 12 were grade 1–2 (10 HER2 +, 2 TN); 28 were grade 3 (7 HER2+, 6 TN, 15 estrogen receptor-positive (ER+)/HER2−). The high-risk group had larger tumors and more often had ductal histology and lymphovascular invasion than the low-risk group and was more likely to undergo mastectomy (18 vs. 5%, p = 0.02), radiotherapy (55 vs. 36%, p = 0.03), and chemotherapy (10 vs. 0%, p = 0.002). Endocrine therapy use was similar among ER+ patients in both groups. The four patients in the high-risk group given chemotherapy were HER2+ and received trastuzumab-based regimens, without any reported toxicities. At median follow-up of 67 months, 10% of the high-risk group had a recurrence (3 distant-only, 1 simultaneous locoregional and distant in a patient treated with mastectomy without radiotherapy). Conclusions Tailored locoregional and systemic therapy resulted in low incidence of failure in these octogenarians with high-risk cancers with low morbidity. Modern adjuvant therapies should be considered for elderly women with high-risk cancers in the absence of significant comorbidities.